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Wkly Epidemiol Rec. Yellow fever in Africa and Central and South America, 2008?2009
Yellow fever in Africa and Central and South America, 2008?2009 (WHO WER, Jan 21 2011, edited)
[Source: World Health Organization, full PDF document (LINK). Edited.]
Weekly epidemiological record
Relev? ?pid?miologique hebdomadaire
21 JANUARY 2011, 86th YEAR / 21 JANVIER 2011, 86e ANN?E
No. 4, 2011, 86, 25?36
Yellow fever in Africa and Central and South America, 2008?2009
Overview
In 2008, 149 laboratory confirmed cases of yellow fever including 58 deaths were reported to WHO; in 2009, 75 laboratory confirmed cases including 21 deaths were reported (Tables 1?4). In 2008, 16 yellow fever outbreaks were reported from 13 countries; C?te d?Ivoire and Paraguay reported outbreaks in the urban areas of their capitals.
In 2009, the number of reported outbreaks decreased to 11. The Central African Republic, C?te d?Ivoire and Guinea were affected by several outbreaks during 2008?2009, reflecting intense virus circulation across the western and central parts of Africa.
In Africa, the Central African Republic reported multiple outbreak events in 2008 and 2009. The term ?event? refers to any cluster of ≥1 laboratory confirmed cases and other cases associated with the suspected cases. This term is used to characterize the risk of an outbreak since, generally, the number of cases is underestimated and a single case often reflects a cluster of undiagnosed cases. A special protocol for conducting risk assessments in the field has been developed in order to measure the circulation of yellow fever virus at the national level, in humans, nonhuman primates and vectors.
Since October 2008, the WHO Region of the Americas has observed an increase in the circulation of sylvatic yellow fever virus; this has affected Argentina and Brazil in the southern part of the continent, the Bolivarian Republic of Venezuela and Colombia in the Andean region, and Trinidad and Tobago in the Caribbean. A large epizootic was reported in Argentina, the Bolivarian Republic of Venezuela, Brazil, and Trinidad and Tobago in 2008.
Risks to travellers
Yellow fever is a major public health problem in large parts of Africa, and Central and South America. Millions of travellers visit areas where the yellow fever virus is present, and they are at risk of becoming infected. No specific treatment is available, and vector control that targets wild mosquitoes in forested areas is not practical for preventing sylvatic infections.
For unvaccinated individuals entering an area of epidemic activity in Africa, the risk of developing yellow fever illness during a 2-week trip has been estimated at 1/2767 unvaccinated people; the risk of dying is 1/1333. The risk varies considerably according to the season.
The corresponding figures for South America are likely to be 10 times lower.
African Region
Summary
In 2008, 47 cases of yellow fever including 6 deaths were reported from the WHO African Region, giving a casefatality rate (CFR) of 12.8% (Table 1); in 2009, 20 cases and 3 deaths were reported, giving a CFR of 15.0% (Table 2). In 2008, C?te d?Ivoire reported urban cases in different health districts in the capital, Abidjan. Although a mass vaccination campaign was conducted in 2001, vaccine coverage was assessed to be ≤60%. The number of cases reported usually reflects only those that have been confirmed by laboratory testing, not the total number of cases that may have occurred.
Burkina Faso
In October 2008, the epidemiological monitoring system in the country detected 2 suspected cases in the health district of Ouahigouya, in the northern part of the country where it borders the southern part of Mali. Both cases were confirmed by laboratory testing. The first case occurred in a boy aged 7 months in the village of Bossawassa; clinical signs included fever and jaundice.
The second case occurred in a boy aged 6 years in the village of Bouadkouli. The 2 villages are contiguous (<2 km apart). A preventive mass vaccination campaign targeted 366 052 people. The administrative vaccine coverage rate was 95%.
Cameroon
In October 2008, the country?s epidemiological monitoring system detected 2 suspected cases, both later confirmed by laboratory testing, in the health districts of Abong Mbang and Ngu?l?mendouka; these districts are in the eastern region. The first case occurred in a 28-year-old man who had not been vaccinated; he was hospitalized in the Abong Mbang district hospital, and died days later of multi-organ failure. The second case occurred in a 45-year-old man who had not been vaccinated; he presented with jaundice, fever and gastrointestinal haemorrhage and he also died. An outbreak investigation team found no other cases. The Ministry of Health decided to vaccinate people in the 2 health districts, and about 125 000 people were vaccinated at the beginning of 2009. The administrative vaccine coverage rate was 92.1%.
In May 2009, the country carried out a national preventive vaccination campaign in 62 districts considered to be at high risk of an epidemic because outbreaks had occurred in other areas of the country. On 8 September 2009, Cameroon reported another laboratory confirmed case, a 61-year-old man who presented with fever, jaundice and back pain. The patient was from Kotto 1, Bomboko village, Buea health district, in the South-West province. The Buea health district had not been known to be endemic for yellow fever. A reactive mass vaccination campaign was conducted in Buea district and Mbongue district (a neighbouring district considered to be at risk), targeting a population of 165 138 people; the administrative coverage rate was 102.5%.
Central African Republic
In 2008, the Central African Republic reported 3 outbreak events. The first was reported in April 2008 in Bozoum subprefecture of the Ouham-Pend? prefecture. The case, a 55-year-old man, was detected by the epidemiological monitoring system; he presented with fever and jaundice, and yellow fever was confirmed by laboratory testing. An outbreak investigation team collected 39 serum samples from symptomatic and asymptomatic contacts of the index case. Only 1 additional sample was confirmed to be positive for yellow fever immunoglobulin M (IgM) by enzyme-linked immunosorbent assay (ELISA). A reactive mass vaccination campaign in Bozoum subprefecture targeted 55 035 people. The reported coverage rate was 92%.
The second outbreak event was reported in August 2008 in Boda subprefecture, La Lobaye prefecture; it was detected by the epidemiological monitoring system. The index case was a 32-year-old man. An outbreak investigation team visited the subprefecture and collected 35 serum samples from symptomatic and asymptomatic people in neighbouring households as well as the index case. All 34 suspected cases were negative for yellow fever IgM by ELISA. A preventive mass vaccination campaign covered 5 subprefectures (4 from La Lobaye and 1 from neighbouring La Sangha prefecture) and targeted 183 992 people. The reported coverage rate was 78.4%.
The third outbreak was reported in December 2008. It occurred at the same time in 2 places: Bimbo subprefecture, Ombella-Mpoko prefecture, in the south of the country and Bria subprefecture, Haute Kotto prefecture, in the north. In Bimbo, the index case was a 38-year-old woman detected by the epidemiological monitoring system on 18 October. The case was confirmed by laboratory testing at the national and regional levels. The Ministry of Health decided to vaccinate people in the geographical areas of Boali and Damarra, 2 districts in the Ombella-Mpoko prefecture, targeting 201 608 people. The reported coverage rate was 94.7%. The index case in Bria was a 31-year-old man with fever and jaundice detected on 24 October 2008. The case was confirmed
by laboratory testing. The Ministry of Health decided to vaccinate people in the geographical areas of Bria, Ouadda and Yalinga, 3 districts in the Haute Kotto prefecture, targeting 297 127 people. The reported coverage rate was 76%.
In November 2009, the Central African Republic reported 4 laboratory confirmed cases including 3 deaths in Yalok?-Bossembelle subprefecture, Ombella-Mpoko prefecture, and in Bagamongone subprefecture, La Lobaye prefecture. The index case was reported in Yalok?-Bossembelle. The patient was a male cattle breeder aged 18 years. During the investigation, serum samples were collected from 80 contacts of the index case; all were negative for yellow fever IgM. Entomological studies showed a limited presence of mosquito vectors of sylvatic yellow fever. A reactive vaccination campaign targeted 327 877 people. The reported coverage rate was 85.4%.
These events occurred in a country where the last outbreak had been reported 24 years earlier, so it was decided to investigate whether there had been an increase in the circulation of yellow fever virus among humans, nonhuman primates and mosquitoes. The investigation concluded that: (i) the risk of an epidemic is great in Bangui, the capital, (in terms of vectors, proportion of population that has not been immunized and virus circulation); (ii) ecological areas in the south are at high risk of epidemics; (iii) ecological areas in the north of the country are at low risk, but there is evidence of virus circulation and there have been some infections recently; (iv) yellow fever is endemic in the country, and there is a risk of epidemics, particularly in urban areas.
Chad
In May 2009 a suspected case was reported by the epidemiological surveillance system in the Iriba district of Wadi Fira region, an area with serious security problems and where there are refugees from Sudan. An outbreak investigation team assessed the situation and reported 2 other suspected cases; these were not confirmed by laboratory testing. For security reasons no reactive campaign was implemented. Chad had implemented yellow fever vaccination campaigns during 1930?1950, and no cases have been reported since then.
C?te d?Ivoire
In May 2008, the Ministry of Health declared there was an an urban outbreak of yellow fever in Abidjan. A mission from the Global Outbreak Alert and Response Network was deployed to assess the epidemiological and entomological situation, and to investigate the risk of a full-scale urban outbreak. Two cases were confirmed in different health districts in the capital. One case occurred in a 48-year-old woman from Cocody, Abidjan; she had been vaccinated in 1997. The second case occurred in a 20-year-old man from the urban area of Treichville in Abidjan; he had never been vaccinated against yellow fever.
The mission concluded that: (i) the epidemiological situation was that of a temporal cluster of cases without geographical focus and without continuation; (ii) although a mass vaccination campaign had been conducted in 2001, actual vaccination coverage is likely to have been ≤60%; (iii) vectors capable of transmitting yellow fever are present in Abidjan; and (iv) the entomological risk indices (Breteau and container index) were above the threshold in all localities investigated, indicating a high risk of transmission. On the basis of these results, the Ministry of Health decided to carry out a vaccination campaign in Abidjan in August 2008, targeting 1 938 161 people. The administrative coverage rate was 105.1%.
In November 2009, C?te d?Ivoire reported 10 suspected cases and 6 deaths in the Minignan and Madinani health districts in the Denguele region. The index case was a 12-year-old male student from Minignan who had not been vaccinated. Two further cases were reported from the Madinani district. After an investigation, only 3 cases were confirmed by testing at the regional reference laboratory using polymerase chain reaction (PCR).
After further investigation, the Ministry of Health vaccinated 154 941 people in the Madinani and Minignan health districts. The administrative vaccine coverage rate was 87.4%.
Democratic Republic of the Congo
In April 2009, the Democratic Republic of the Congo reported 1 case, a 55-year-old male farmer living in Mbama district, Cuvette West department. He initially presented with acute abdominal pain, and subsequently developed fever and jaundice. An outbreak-investigation team assessed the situation in the district, and no further cases were detected. A population of 74 697 people was targeted for vaccination, and reported coverage was 71.5%. The country had implemented mass vaccination campaigns during 1930?1960. The last reported outbreak occurred in 1981, and no cases had been confi rmed until 2009.
Guinea
In September 2008, the Ministry of Health reported 2 laboratory confirmed cases in N?z?r?kor? prefecture. The first case occurred in a 24-year-old man living in Bounouma subprefecture. The second case occurred in another 24-year-old man in N?z?r?kor? Urbain Commune. Both cases had not been vaccinated. An outbreak investigation team visited 10 subprefectures and the N?z?r?kor? Urbain Commune, and 2 subprefectures in Lola prefecture. The mission concluded that: (i) using the case definition, 14 suspected cases could be identified retrospectively, and 1 of these had died after presenting with fever and jaundice; (ii) most of the prefectures had vaccinated their populations in 2005, and coverage was reported to be 95.2%; (iii) the only areas where a low coverage rate was reported (45%) were Bounama subprefecture, the urbain commune and the Ivorian refugee camp in Kouankan II. The Ministry of Health implemented a reactive vaccination campaign in these 3 areas, and targeted 140 342 people. The reported administrative coverage rate was 101%.
In December 2008, Guinea reported 2 laboratory confirmed cases in the Faranah health district. Both cases presented with fever and jaundice, and were reported by the surveillance system. The index case was a 40-yearold man from Faranah Koura; the second was a 40-yearold man from Nianfourando sector; both localities are part of the Faranah centre area. An additional 21 suspected cases were reported, of which 3 died. A reactive vaccination campaign targeted 60 485 people; the coverage rate was not reported.
In January 2009, Guinea reported a suspected case of yellow fever in Mandiana prefecture, Kankan region.
The case occurred in a 35-year-old woman from the village of Malikila who presented with fever and jaundice. A further 2 laboratory confirmed cases and 6 suspected cases were identifi ed. A reactive vaccination campaign in 12 subprefectures targeted 290 292 people; a survey found the coverage rate to be 94.8%. Mandiana prefecture is 1 of the 25 prefectures in the country considered to be at highest risk for yellow fever.
Liberia
In April 2008, 2 laboratory confirmed cases of yellow fever were reported, including 1 death in Tappita district, Nimba county. The index case was a 32-year-old man who died. A reactive mass vaccination campaign in the affected and surrounding districts was conducted, targeting 294 613 people. The administrative coverage rate was 99%.
In April 2009, Liberia reported 1 laboratory confirmed case in Luyeama town, Zorzor district. The case was identified through regular yellow fever surveillance in Lofa county. The case occurred in a 32-year-old man who presented with fever and jaundice.
During the investigation of the outbreak, 9 serum samples from suspected cases and contacts were collected, but no additional cases were identified. A reactive campaign in the Zorzor and Voinjama districts was organized, targeting 96 169 people. The administrative coverage rate was 99.7%.
Sierra Leone
In December 2008, the Ministry of Health reported 2 laboratory confirmed cases in the Gerihun and Jembe communities, Bo district. Both cases were reported by the surveillance system; both patients presented with fever and jaundice. During the investigation of the outbreak, 7 additional clinical suspected cases were identified but none was confi rmed by laboratory testing. A reactive vaccination campaign targeting 527 978 people was carried out in Bo district. The administrative coverage rate was 84%.
In the African Region in 2008, 10 reactive campaigns targeted 4 million people; in 2009, 6 reactive campaigns targeted 1.1 million people.
Risk assessment and preventive campaigns in West Africa
Between 2006 and 2009, 10 countries in West Africa benefited from a risk assessment for yellow fever. Entomological research may be conducted if warranted. The models used for the risk assessments account for the vulnerability of the population to vector-borne diseases and provide insight into the dynamics of the disease and the risk of epidemics.
The risk analysis is a 2-stage process: first, exposure and susceptibility indicators in rural and urban areas are modelled; second, local stakeholders add information to the outcomes of the modelling. The analysis is enhanced by the inclusion of factors that cannot be addressed by mathematical modelling, such as the migration patterns of nomadic populations.
In West Africa in 2008, 2 preventive vaccination campaigns were organized in Burkina Faso and Mali, targeting 13.5 million people. In 2009, 4 preventive campaigns were organized in Benin, Cameroon, Liberia and Sierra Leone, targeting 20.8 million people.
Region of the Americas
Summary
In 2008, 102 cases of yellow fever including 52 deaths were reported by Argentina, Bolivia, Brazil, Colombia, Paraguay and Peru; the CFR was 51%. In 2009, 55 cases including 18 deaths were reported by the same countries; the CFR was 32.7% (Table 3).
In 2008, cases were identified in an urban environment in Asunci?n, Paraguay. These were the fi rst cases reported from an urban area in the Region of the Americas since 1954, when a case of urban yellow fever was reported by Trinidad and Tobago. Before that, the last outbreak of urban yellow fever had been reported by Brazil in 1942.
Epidemiological surveillance has intensified in recent years in the Region of the Americas. Argentina, the Bolivarian Republic of Venezuela, Brazil and Paraguay are carrying out surveillance for yellow fever deaths among nonhuman primates in addition to surveillance for icterohaemorrhagic fever. The strengthening of surveillance has contributed to the early detection of circulating virus and to redefining enzootic areas on the continent.
Argentina
Between February and March 2008, 8 cases in humans including 1 death were confirmed by laboratory testing and reported by Misiones province. Four cases, including the death, occurred in Guarani department. The remaining 4 cases were diagnosed in the departments of San Pedro (2), Eldorado (1) and General Belgrano (1). In December 2008, another fatal case, confirmed by laboratory testing, was reported by Capital department, Misiones province. This outbreak was the first yellow fever event reported by the country since 1966.
Of these 9 cases, 8 (89%) occurred among males, with an age range of 16?61 years. All cases occurred among people who worked in rural areas; none of them had been vaccinated.
In early January 2008, several dead monkeys were reported in the departments of Apostoles, Capital y Concepci?n, Guaran? and San Pedro, all of which are in Misiones province. No cases were reported in 2009.
Plurinational State of Bolivia
In the Plurinational State of Bolivia, only 1 laboratory confirmed case was reported in 2008; it occurred in an unvaccinated 19-year-old male farm worker, who survived. The probable place of infection was the municipality of Palos Blancos, located in the tropical area of La Paz department. No cases were reported in 2009.
Brazil
In 2008, Brazil reported a total of 46 confirmed cases including 27 deaths (CFR, 58.7%). Of these, 43 cases were part of a widespread outbreak that involved 7 states in the central and southern regions of the country, and persisted throughout the year. The first 3 cases were detected in late December 2007.
The outbreak continued during 2008, when the country reported 43 additional cases in the states of Distrito Federal (5), Goi?s (17), Minas Gerais (1), Mato Grosso (2), Mato Grosso do Sul (9), Parana (2), Rio Grande Do Sul (5) and S?o Paulo (2). There were 25 fatalities among the 43 reported cases in this outbreak, giving a CFR of 58%. Two cases were confirmed by epidemiological linkage; the remaining 41 were confirmed by laboratory testing. The majority of cases occurred among unvaccinated men (median age, 38 years) who had been exposed to the sylvatic cycle of the virus. Of the 41 cases confirmed by testing, 10 (23%) occurred in females, and 5(12%) had been vaccinated.
The last case occurred at the end of May 2008.
Three additional cases, unrelated to the outbreak and not epidemiologically linked, were reported by Para state. One occurred in February 2008; 2 occurred during June 2008.
In 2009, 43 cases were reported including 15 deaths in S?o Paulo and Rio Grande do Sul states. In S?o Paulo state, 27 laboratory confirmed cases were reported from February to April 2009; 10 of these died (CFR, 37%).
Among the 27 confirmed cases, 17 (63%) occurred in males. The age range of all cases was 8 days to 52 years (median age, 29 years); none of the cases had been vaccinated and all were involved in rural activities or lived in rural areas. Cases were reported from the following municipalities: Buri, Italinga, Piraju, Sarutai? and Tejupa.
In the state of Rio Grande do Sul, 13 cases were reported (11 confirmed by laboratory testing; 2 suspected and linked epidemiologically). Among these 13 cases, 3 died (CFR, 23%); 11 cases (84.6%) occurred in males. Cases were reported from the following municipalities: Espumoso, Iju?, Santo Angelo, Santa Cruz do Sul, Vera Cruz and Vale Verde.
During 2008, the virus was circulating in nonhuman primates in the central and south-eastern regions of the country; this was followed by the human outbreak of sylvatic yellow fever during 2008?2009.
Colombia
In 2008, Colombia reported 3 laboratory confirmed cases (CFR, 100%). The cases occurred in Guaviare and Meta departments. The first case occurred in a 52-year old man who had not been vaccinated; he had visited El Retorno municipality in Guaviare department. The second case occurred in a 21-year-old housewife who lived in Puerto Gaitan and had not been vaccinated. The last case was identified in Puerto Concordia municipality; it occurred in a 24-year-old male farmer whose vaccination status was unknown.
In 2009, 5 laboratory confirmed cases in humans were reported; they were probably infected in Meta department, 4 in La Macarena municipality and 1 in Puerto Concordia municipality. Two of the cases died (CFR, 40%): 1 was an autochthonous tourist and the other was a farmer. Of these 5 cases, 4 (80%) occurred in males.
The age range of cases was 17?55 years. One case had been immunized in 2004; he had mild symptoms and made a full recovery. In the case who had been vaccinated, laboratory tests were negative for IgM but PCR was positive. Vaccination status was unknown for 2 cases; 2 cases had not been vaccinated.
Paraguay
In January 2008, a suspected case of yellow fever was admitted to a hospital in San Pedro state and later confirmed by laboratory testing. The patient had taken a hunting trip with 6 people to a jungle area in the neighbouring municipality of San Estanislao. Among his hunting companions, 3 also developed symptoms compatible with yellow fever infection; they tested positive.
This was the first identified outbreak of the disease in Paraguay since 1974.
Through the end of May 2008, another 28 laboratory confirmed cases were found. In 2008, cases were reported from the departments of San Pedro (15), Central (9) and Caaguazu (4); these were identified as a result of intense surveillance that had been implemented countrywide. There were 11 deaths among the 28 cases (CFR, 39.3%). A total of 17 cases (80%) occurred in males. The median age of the 28 cases was 26 years. The main activities of the cases were farming and hunting.
All 9 cases identified in Central department were residents of Laurelty, an urban neighbourhood that is part of metropolitan Asunci?n, the capital of Paraguay. Five (56%) cases occurred in females. The age range of all cases was 11?39 years. All cases worked in metropolitan Asunci?n and did not have a history of recent travel outside their area of residence. The households of the cases were located within a 500 meter radius of one another. In this cluster, 3 cases were fatal (CFR, 33.3%).
An entomological investigation carried out during January indicated that the household infestation rate with Aedes aegypti was 13%. Sylvatic mosquitoes were not found, and the residents denied the presence of sylvatic primates.
A panel of experts organized by the Pan American Health Organization, at the request of the Ministry of Health, concluded that the epidemiological and entomological characteristics of the outbreak were of an urban outbreak transmitted by Aedes aegypti. With support from the International Coordinating Group for Yellow Fever Vaccine Provision, a reactive vaccination campaign in San Lorenzo and Asunci?n cities targeted 1 852 888 people; the coverage rate was not reported. This outbreak of yellow fever in an urban area represents the first occurrence in the American continent since 1942. Given that many cities in the Region of the Americas have been re-infested by Aedes aegypti mosquitoes, outbreaks in urban areas continue to pose a serious public health threat.
Peru
During 2008, 15 cases were confirmed by laboratory testing in Peru (CFR, 60%). The cases occurred in the departments of Amazonas (7), San Martin (5), Cusco (1), Madre de Dios (1) and Loreto (1). Of these, 12 (80%) occurred in males. The age range for all cases was 2?58 years. None of the cases had been vaccinated. In 2009, 8 cases including 5 deaths were reported (7 cases confirmed by laboratory; 1 by epidemiological linkage); the CFR was 62.5%. Cases were reported in the following departments: Cusco (1 case), Loreto (1) and San Martin (6). All 7 confirmed cases occurred in males.
The age range of all cases was 12?43 years. Seven cases had not been vaccinateded; the vaccination status of the other case was unknown.
Immunization and vaccine coverage in the Region of the Americas
Most countries with enzootic areas in the Region of the Americas introduced yellow fever vaccine into their routine immunization schedules in 2000. Notably, Panama started vaccinating against yellow fever routinely in 1974, and Guyana did so in 1980. As of 2009, 8 countries with enzootic areas had introduced the vaccine into their national immunization schedules for all children at age 1 year, which is the same time that children receive measles?mumps?rubella (MMR) vaccine; these countries are the Plurinational State of Bolivia, the Bolivarian Republic of Venezuela, Colombia, Guyana, Paraguay, Peru, and Trinidad and Tobago. Yellow fever vaccine is administered to children at age 9 months in Brazil and French Guiana; Ecuador, Panama, and Suriname vaccinate in enzootic areas.
Paraguay had introduced vaccination into areas bordering enzootic municipalities in neighbouring countries in 2001; Argentina did so in 2002. In 2007, Paraguay decided to make yellow fever vaccination universal.
Coverage of routine yellow fever vaccination among children has varied over time and by country, but coverage for this vaccine is often lower than coverage for MMR vaccine.
Supplementary vaccination activities have varied among countries, conducted either as campaigns following outbreaks or as preventive campaigns. In 2004, Peru started implementing a plan aimed at vaccinating 11 975 137 people in endemic areas aged 2?59 years and migrants to those areas. By the end of 2008, the country had vaccinated approximately 11 million people, reaching an average coverage rate of 98%, which was verified by rapid monitoring of coverage in all regions included in the national plan.
Following an outbreak in 2008 that extended from Brazil to Paraguay and to northern Argentina, Paraguay conducted a vaccination campaign aimed at people aged >1 year living in an affected area or a surrounding area; a total of 3.5 million people were vaccinated.
Argentina also carried out mass campaigns during the first quarter of 2008; close to 1.4 million people were vaccinated. The increase in yellow fever activity in the Region of the Americas in 2008 led to a worldwide shortage of yellow fever vaccines.
Epizootics in the Region of the Americas
During 2008 and 2009 some countries carried out surveillance of deaths among primates. Their reports led to the confi rmation of several epizootics.
In November 2007 in Argentina, a laboratory confirmed epizootic was identifi ed in Iguazu department, Misiones province. In early January 2008, several dead monkeys were reported in the departments of Apostoles, Capital y Concepci?n, Guaran? and San Pedro, all of which are in Misiones province. Further epizootics were confirmed in this province in October 2008, when 8 dead monkeys were reported near El Soberbio locality, and in December 2008, when 6 dead monkeys were notifi ed in the municipalities of Az?l, Cerro, Garup? and San Jos? in Misiones province.
In Brazil in 2007, intense circulation of the virus in nonhuman primates was identified in the central and southeastern regions of the country; this was followed by the human outbreak of sylvatic yellow fever described earlier.
The epizootic continued to be seen in the same area during 2008.
In Brazil in October 2008, dead monkeys were also reported in the north-western part of Rio Grande do Sul state. Active surveillance has been implemented, and more epizootic areas have been found in places previously considered to be non-enzootic. This finding led national authorities to carry out an extensive vaccination campaign throughout almost all of Rio Grande do Sul.
Circulation of sylvatic yellow fever virus continued throughout 2009 in Brazil, causing more epizootic cases (especially in Rio Grande do Sul state) and human cases.
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[Source: World Health Organization, full PDF document (LINK). Edited.]
Weekly epidemiological record
Relev? ?pid?miologique hebdomadaire
21 JANUARY 2011, 86th YEAR / 21 JANVIER 2011, 86e ANN?E
No. 4, 2011, 86, 25?36
Yellow fever in Africa and Central and South America, 2008?2009
Overview
In 2008, 149 laboratory confirmed cases of yellow fever including 58 deaths were reported to WHO; in 2009, 75 laboratory confirmed cases including 21 deaths were reported (Tables 1?4). In 2008, 16 yellow fever outbreaks were reported from 13 countries; C?te d?Ivoire and Paraguay reported outbreaks in the urban areas of their capitals.
In 2009, the number of reported outbreaks decreased to 11. The Central African Republic, C?te d?Ivoire and Guinea were affected by several outbreaks during 2008?2009, reflecting intense virus circulation across the western and central parts of Africa.
In Africa, the Central African Republic reported multiple outbreak events in 2008 and 2009. The term ?event? refers to any cluster of ≥1 laboratory confirmed cases and other cases associated with the suspected cases. This term is used to characterize the risk of an outbreak since, generally, the number of cases is underestimated and a single case often reflects a cluster of undiagnosed cases. A special protocol for conducting risk assessments in the field has been developed in order to measure the circulation of yellow fever virus at the national level, in humans, nonhuman primates and vectors.
Since October 2008, the WHO Region of the Americas has observed an increase in the circulation of sylvatic yellow fever virus; this has affected Argentina and Brazil in the southern part of the continent, the Bolivarian Republic of Venezuela and Colombia in the Andean region, and Trinidad and Tobago in the Caribbean. A large epizootic was reported in Argentina, the Bolivarian Republic of Venezuela, Brazil, and Trinidad and Tobago in 2008.
Risks to travellers
Yellow fever is a major public health problem in large parts of Africa, and Central and South America. Millions of travellers visit areas where the yellow fever virus is present, and they are at risk of becoming infected. No specific treatment is available, and vector control that targets wild mosquitoes in forested areas is not practical for preventing sylvatic infections.
For unvaccinated individuals entering an area of epidemic activity in Africa, the risk of developing yellow fever illness during a 2-week trip has been estimated at 1/2767 unvaccinated people; the risk of dying is 1/1333. The risk varies considerably according to the season.
The corresponding figures for South America are likely to be 10 times lower.
African Region
Summary
In 2008, 47 cases of yellow fever including 6 deaths were reported from the WHO African Region, giving a casefatality rate (CFR) of 12.8% (Table 1); in 2009, 20 cases and 3 deaths were reported, giving a CFR of 15.0% (Table 2). In 2008, C?te d?Ivoire reported urban cases in different health districts in the capital, Abidjan. Although a mass vaccination campaign was conducted in 2001, vaccine coverage was assessed to be ≤60%. The number of cases reported usually reflects only those that have been confirmed by laboratory testing, not the total number of cases that may have occurred.
Burkina Faso
In October 2008, the epidemiological monitoring system in the country detected 2 suspected cases in the health district of Ouahigouya, in the northern part of the country where it borders the southern part of Mali. Both cases were confirmed by laboratory testing. The first case occurred in a boy aged 7 months in the village of Bossawassa; clinical signs included fever and jaundice.
The second case occurred in a boy aged 6 years in the village of Bouadkouli. The 2 villages are contiguous (<2 km apart). A preventive mass vaccination campaign targeted 366 052 people. The administrative vaccine coverage rate was 95%.
Cameroon
In October 2008, the country?s epidemiological monitoring system detected 2 suspected cases, both later confirmed by laboratory testing, in the health districts of Abong Mbang and Ngu?l?mendouka; these districts are in the eastern region. The first case occurred in a 28-year-old man who had not been vaccinated; he was hospitalized in the Abong Mbang district hospital, and died days later of multi-organ failure. The second case occurred in a 45-year-old man who had not been vaccinated; he presented with jaundice, fever and gastrointestinal haemorrhage and he also died. An outbreak investigation team found no other cases. The Ministry of Health decided to vaccinate people in the 2 health districts, and about 125 000 people were vaccinated at the beginning of 2009. The administrative vaccine coverage rate was 92.1%.
In May 2009, the country carried out a national preventive vaccination campaign in 62 districts considered to be at high risk of an epidemic because outbreaks had occurred in other areas of the country. On 8 September 2009, Cameroon reported another laboratory confirmed case, a 61-year-old man who presented with fever, jaundice and back pain. The patient was from Kotto 1, Bomboko village, Buea health district, in the South-West province. The Buea health district had not been known to be endemic for yellow fever. A reactive mass vaccination campaign was conducted in Buea district and Mbongue district (a neighbouring district considered to be at risk), targeting a population of 165 138 people; the administrative coverage rate was 102.5%.
Central African Republic
In 2008, the Central African Republic reported 3 outbreak events. The first was reported in April 2008 in Bozoum subprefecture of the Ouham-Pend? prefecture. The case, a 55-year-old man, was detected by the epidemiological monitoring system; he presented with fever and jaundice, and yellow fever was confirmed by laboratory testing. An outbreak investigation team collected 39 serum samples from symptomatic and asymptomatic contacts of the index case. Only 1 additional sample was confirmed to be positive for yellow fever immunoglobulin M (IgM) by enzyme-linked immunosorbent assay (ELISA). A reactive mass vaccination campaign in Bozoum subprefecture targeted 55 035 people. The reported coverage rate was 92%.
The second outbreak event was reported in August 2008 in Boda subprefecture, La Lobaye prefecture; it was detected by the epidemiological monitoring system. The index case was a 32-year-old man. An outbreak investigation team visited the subprefecture and collected 35 serum samples from symptomatic and asymptomatic people in neighbouring households as well as the index case. All 34 suspected cases were negative for yellow fever IgM by ELISA. A preventive mass vaccination campaign covered 5 subprefectures (4 from La Lobaye and 1 from neighbouring La Sangha prefecture) and targeted 183 992 people. The reported coverage rate was 78.4%.
The third outbreak was reported in December 2008. It occurred at the same time in 2 places: Bimbo subprefecture, Ombella-Mpoko prefecture, in the south of the country and Bria subprefecture, Haute Kotto prefecture, in the north. In Bimbo, the index case was a 38-year-old woman detected by the epidemiological monitoring system on 18 October. The case was confirmed by laboratory testing at the national and regional levels. The Ministry of Health decided to vaccinate people in the geographical areas of Boali and Damarra, 2 districts in the Ombella-Mpoko prefecture, targeting 201 608 people. The reported coverage rate was 94.7%. The index case in Bria was a 31-year-old man with fever and jaundice detected on 24 October 2008. The case was confirmed
by laboratory testing. The Ministry of Health decided to vaccinate people in the geographical areas of Bria, Ouadda and Yalinga, 3 districts in the Haute Kotto prefecture, targeting 297 127 people. The reported coverage rate was 76%.
In November 2009, the Central African Republic reported 4 laboratory confirmed cases including 3 deaths in Yalok?-Bossembelle subprefecture, Ombella-Mpoko prefecture, and in Bagamongone subprefecture, La Lobaye prefecture. The index case was reported in Yalok?-Bossembelle. The patient was a male cattle breeder aged 18 years. During the investigation, serum samples were collected from 80 contacts of the index case; all were negative for yellow fever IgM. Entomological studies showed a limited presence of mosquito vectors of sylvatic yellow fever. A reactive vaccination campaign targeted 327 877 people. The reported coverage rate was 85.4%.
These events occurred in a country where the last outbreak had been reported 24 years earlier, so it was decided to investigate whether there had been an increase in the circulation of yellow fever virus among humans, nonhuman primates and mosquitoes. The investigation concluded that: (i) the risk of an epidemic is great in Bangui, the capital, (in terms of vectors, proportion of population that has not been immunized and virus circulation); (ii) ecological areas in the south are at high risk of epidemics; (iii) ecological areas in the north of the country are at low risk, but there is evidence of virus circulation and there have been some infections recently; (iv) yellow fever is endemic in the country, and there is a risk of epidemics, particularly in urban areas.
Chad
In May 2009 a suspected case was reported by the epidemiological surveillance system in the Iriba district of Wadi Fira region, an area with serious security problems and where there are refugees from Sudan. An outbreak investigation team assessed the situation and reported 2 other suspected cases; these were not confirmed by laboratory testing. For security reasons no reactive campaign was implemented. Chad had implemented yellow fever vaccination campaigns during 1930?1950, and no cases have been reported since then.
C?te d?Ivoire
In May 2008, the Ministry of Health declared there was an an urban outbreak of yellow fever in Abidjan. A mission from the Global Outbreak Alert and Response Network was deployed to assess the epidemiological and entomological situation, and to investigate the risk of a full-scale urban outbreak. Two cases were confirmed in different health districts in the capital. One case occurred in a 48-year-old woman from Cocody, Abidjan; she had been vaccinated in 1997. The second case occurred in a 20-year-old man from the urban area of Treichville in Abidjan; he had never been vaccinated against yellow fever.
The mission concluded that: (i) the epidemiological situation was that of a temporal cluster of cases without geographical focus and without continuation; (ii) although a mass vaccination campaign had been conducted in 2001, actual vaccination coverage is likely to have been ≤60%; (iii) vectors capable of transmitting yellow fever are present in Abidjan; and (iv) the entomological risk indices (Breteau and container index) were above the threshold in all localities investigated, indicating a high risk of transmission. On the basis of these results, the Ministry of Health decided to carry out a vaccination campaign in Abidjan in August 2008, targeting 1 938 161 people. The administrative coverage rate was 105.1%.
In November 2009, C?te d?Ivoire reported 10 suspected cases and 6 deaths in the Minignan and Madinani health districts in the Denguele region. The index case was a 12-year-old male student from Minignan who had not been vaccinated. Two further cases were reported from the Madinani district. After an investigation, only 3 cases were confirmed by testing at the regional reference laboratory using polymerase chain reaction (PCR).
After further investigation, the Ministry of Health vaccinated 154 941 people in the Madinani and Minignan health districts. The administrative vaccine coverage rate was 87.4%.
Democratic Republic of the Congo
In April 2009, the Democratic Republic of the Congo reported 1 case, a 55-year-old male farmer living in Mbama district, Cuvette West department. He initially presented with acute abdominal pain, and subsequently developed fever and jaundice. An outbreak-investigation team assessed the situation in the district, and no further cases were detected. A population of 74 697 people was targeted for vaccination, and reported coverage was 71.5%. The country had implemented mass vaccination campaigns during 1930?1960. The last reported outbreak occurred in 1981, and no cases had been confi rmed until 2009.
Guinea
In September 2008, the Ministry of Health reported 2 laboratory confirmed cases in N?z?r?kor? prefecture. The first case occurred in a 24-year-old man living in Bounouma subprefecture. The second case occurred in another 24-year-old man in N?z?r?kor? Urbain Commune. Both cases had not been vaccinated. An outbreak investigation team visited 10 subprefectures and the N?z?r?kor? Urbain Commune, and 2 subprefectures in Lola prefecture. The mission concluded that: (i) using the case definition, 14 suspected cases could be identified retrospectively, and 1 of these had died after presenting with fever and jaundice; (ii) most of the prefectures had vaccinated their populations in 2005, and coverage was reported to be 95.2%; (iii) the only areas where a low coverage rate was reported (45%) were Bounama subprefecture, the urbain commune and the Ivorian refugee camp in Kouankan II. The Ministry of Health implemented a reactive vaccination campaign in these 3 areas, and targeted 140 342 people. The reported administrative coverage rate was 101%.
In December 2008, Guinea reported 2 laboratory confirmed cases in the Faranah health district. Both cases presented with fever and jaundice, and were reported by the surveillance system. The index case was a 40-yearold man from Faranah Koura; the second was a 40-yearold man from Nianfourando sector; both localities are part of the Faranah centre area. An additional 21 suspected cases were reported, of which 3 died. A reactive vaccination campaign targeted 60 485 people; the coverage rate was not reported.
In January 2009, Guinea reported a suspected case of yellow fever in Mandiana prefecture, Kankan region.
The case occurred in a 35-year-old woman from the village of Malikila who presented with fever and jaundice. A further 2 laboratory confirmed cases and 6 suspected cases were identifi ed. A reactive vaccination campaign in 12 subprefectures targeted 290 292 people; a survey found the coverage rate to be 94.8%. Mandiana prefecture is 1 of the 25 prefectures in the country considered to be at highest risk for yellow fever.
Liberia
In April 2008, 2 laboratory confirmed cases of yellow fever were reported, including 1 death in Tappita district, Nimba county. The index case was a 32-year-old man who died. A reactive mass vaccination campaign in the affected and surrounding districts was conducted, targeting 294 613 people. The administrative coverage rate was 99%.
In April 2009, Liberia reported 1 laboratory confirmed case in Luyeama town, Zorzor district. The case was identified through regular yellow fever surveillance in Lofa county. The case occurred in a 32-year-old man who presented with fever and jaundice.
During the investigation of the outbreak, 9 serum samples from suspected cases and contacts were collected, but no additional cases were identified. A reactive campaign in the Zorzor and Voinjama districts was organized, targeting 96 169 people. The administrative coverage rate was 99.7%.
Sierra Leone
In December 2008, the Ministry of Health reported 2 laboratory confirmed cases in the Gerihun and Jembe communities, Bo district. Both cases were reported by the surveillance system; both patients presented with fever and jaundice. During the investigation of the outbreak, 7 additional clinical suspected cases were identified but none was confi rmed by laboratory testing. A reactive vaccination campaign targeting 527 978 people was carried out in Bo district. The administrative coverage rate was 84%.
In the African Region in 2008, 10 reactive campaigns targeted 4 million people; in 2009, 6 reactive campaigns targeted 1.1 million people.
Risk assessment and preventive campaigns in West Africa
Between 2006 and 2009, 10 countries in West Africa benefited from a risk assessment for yellow fever. Entomological research may be conducted if warranted. The models used for the risk assessments account for the vulnerability of the population to vector-borne diseases and provide insight into the dynamics of the disease and the risk of epidemics.
The risk analysis is a 2-stage process: first, exposure and susceptibility indicators in rural and urban areas are modelled; second, local stakeholders add information to the outcomes of the modelling. The analysis is enhanced by the inclusion of factors that cannot be addressed by mathematical modelling, such as the migration patterns of nomadic populations.
In West Africa in 2008, 2 preventive vaccination campaigns were organized in Burkina Faso and Mali, targeting 13.5 million people. In 2009, 4 preventive campaigns were organized in Benin, Cameroon, Liberia and Sierra Leone, targeting 20.8 million people.
Region of the Americas
Summary
In 2008, 102 cases of yellow fever including 52 deaths were reported by Argentina, Bolivia, Brazil, Colombia, Paraguay and Peru; the CFR was 51%. In 2009, 55 cases including 18 deaths were reported by the same countries; the CFR was 32.7% (Table 3).
In 2008, cases were identified in an urban environment in Asunci?n, Paraguay. These were the fi rst cases reported from an urban area in the Region of the Americas since 1954, when a case of urban yellow fever was reported by Trinidad and Tobago. Before that, the last outbreak of urban yellow fever had been reported by Brazil in 1942.
Epidemiological surveillance has intensified in recent years in the Region of the Americas. Argentina, the Bolivarian Republic of Venezuela, Brazil and Paraguay are carrying out surveillance for yellow fever deaths among nonhuman primates in addition to surveillance for icterohaemorrhagic fever. The strengthening of surveillance has contributed to the early detection of circulating virus and to redefining enzootic areas on the continent.
Argentina
Between February and March 2008, 8 cases in humans including 1 death were confirmed by laboratory testing and reported by Misiones province. Four cases, including the death, occurred in Guarani department. The remaining 4 cases were diagnosed in the departments of San Pedro (2), Eldorado (1) and General Belgrano (1). In December 2008, another fatal case, confirmed by laboratory testing, was reported by Capital department, Misiones province. This outbreak was the first yellow fever event reported by the country since 1966.
Of these 9 cases, 8 (89%) occurred among males, with an age range of 16?61 years. All cases occurred among people who worked in rural areas; none of them had been vaccinated.
In early January 2008, several dead monkeys were reported in the departments of Apostoles, Capital y Concepci?n, Guaran? and San Pedro, all of which are in Misiones province. No cases were reported in 2009.
Plurinational State of Bolivia
In the Plurinational State of Bolivia, only 1 laboratory confirmed case was reported in 2008; it occurred in an unvaccinated 19-year-old male farm worker, who survived. The probable place of infection was the municipality of Palos Blancos, located in the tropical area of La Paz department. No cases were reported in 2009.
Brazil
In 2008, Brazil reported a total of 46 confirmed cases including 27 deaths (CFR, 58.7%). Of these, 43 cases were part of a widespread outbreak that involved 7 states in the central and southern regions of the country, and persisted throughout the year. The first 3 cases were detected in late December 2007.
The outbreak continued during 2008, when the country reported 43 additional cases in the states of Distrito Federal (5), Goi?s (17), Minas Gerais (1), Mato Grosso (2), Mato Grosso do Sul (9), Parana (2), Rio Grande Do Sul (5) and S?o Paulo (2). There were 25 fatalities among the 43 reported cases in this outbreak, giving a CFR of 58%. Two cases were confirmed by epidemiological linkage; the remaining 41 were confirmed by laboratory testing. The majority of cases occurred among unvaccinated men (median age, 38 years) who had been exposed to the sylvatic cycle of the virus. Of the 41 cases confirmed by testing, 10 (23%) occurred in females, and 5(12%) had been vaccinated.
The last case occurred at the end of May 2008.
Three additional cases, unrelated to the outbreak and not epidemiologically linked, were reported by Para state. One occurred in February 2008; 2 occurred during June 2008.
In 2009, 43 cases were reported including 15 deaths in S?o Paulo and Rio Grande do Sul states. In S?o Paulo state, 27 laboratory confirmed cases were reported from February to April 2009; 10 of these died (CFR, 37%).
Among the 27 confirmed cases, 17 (63%) occurred in males. The age range of all cases was 8 days to 52 years (median age, 29 years); none of the cases had been vaccinated and all were involved in rural activities or lived in rural areas. Cases were reported from the following municipalities: Buri, Italinga, Piraju, Sarutai? and Tejupa.
In the state of Rio Grande do Sul, 13 cases were reported (11 confirmed by laboratory testing; 2 suspected and linked epidemiologically). Among these 13 cases, 3 died (CFR, 23%); 11 cases (84.6%) occurred in males. Cases were reported from the following municipalities: Espumoso, Iju?, Santo Angelo, Santa Cruz do Sul, Vera Cruz and Vale Verde.
During 2008, the virus was circulating in nonhuman primates in the central and south-eastern regions of the country; this was followed by the human outbreak of sylvatic yellow fever during 2008?2009.
Colombia
In 2008, Colombia reported 3 laboratory confirmed cases (CFR, 100%). The cases occurred in Guaviare and Meta departments. The first case occurred in a 52-year old man who had not been vaccinated; he had visited El Retorno municipality in Guaviare department. The second case occurred in a 21-year-old housewife who lived in Puerto Gaitan and had not been vaccinated. The last case was identified in Puerto Concordia municipality; it occurred in a 24-year-old male farmer whose vaccination status was unknown.
In 2009, 5 laboratory confirmed cases in humans were reported; they were probably infected in Meta department, 4 in La Macarena municipality and 1 in Puerto Concordia municipality. Two of the cases died (CFR, 40%): 1 was an autochthonous tourist and the other was a farmer. Of these 5 cases, 4 (80%) occurred in males.
The age range of cases was 17?55 years. One case had been immunized in 2004; he had mild symptoms and made a full recovery. In the case who had been vaccinated, laboratory tests were negative for IgM but PCR was positive. Vaccination status was unknown for 2 cases; 2 cases had not been vaccinated.
Paraguay
In January 2008, a suspected case of yellow fever was admitted to a hospital in San Pedro state and later confirmed by laboratory testing. The patient had taken a hunting trip with 6 people to a jungle area in the neighbouring municipality of San Estanislao. Among his hunting companions, 3 also developed symptoms compatible with yellow fever infection; they tested positive.
This was the first identified outbreak of the disease in Paraguay since 1974.
Through the end of May 2008, another 28 laboratory confirmed cases were found. In 2008, cases were reported from the departments of San Pedro (15), Central (9) and Caaguazu (4); these were identified as a result of intense surveillance that had been implemented countrywide. There were 11 deaths among the 28 cases (CFR, 39.3%). A total of 17 cases (80%) occurred in males. The median age of the 28 cases was 26 years. The main activities of the cases were farming and hunting.
All 9 cases identified in Central department were residents of Laurelty, an urban neighbourhood that is part of metropolitan Asunci?n, the capital of Paraguay. Five (56%) cases occurred in females. The age range of all cases was 11?39 years. All cases worked in metropolitan Asunci?n and did not have a history of recent travel outside their area of residence. The households of the cases were located within a 500 meter radius of one another. In this cluster, 3 cases were fatal (CFR, 33.3%).
An entomological investigation carried out during January indicated that the household infestation rate with Aedes aegypti was 13%. Sylvatic mosquitoes were not found, and the residents denied the presence of sylvatic primates.
A panel of experts organized by the Pan American Health Organization, at the request of the Ministry of Health, concluded that the epidemiological and entomological characteristics of the outbreak were of an urban outbreak transmitted by Aedes aegypti. With support from the International Coordinating Group for Yellow Fever Vaccine Provision, a reactive vaccination campaign in San Lorenzo and Asunci?n cities targeted 1 852 888 people; the coverage rate was not reported. This outbreak of yellow fever in an urban area represents the first occurrence in the American continent since 1942. Given that many cities in the Region of the Americas have been re-infested by Aedes aegypti mosquitoes, outbreaks in urban areas continue to pose a serious public health threat.
Peru
During 2008, 15 cases were confirmed by laboratory testing in Peru (CFR, 60%). The cases occurred in the departments of Amazonas (7), San Martin (5), Cusco (1), Madre de Dios (1) and Loreto (1). Of these, 12 (80%) occurred in males. The age range for all cases was 2?58 years. None of the cases had been vaccinated. In 2009, 8 cases including 5 deaths were reported (7 cases confirmed by laboratory; 1 by epidemiological linkage); the CFR was 62.5%. Cases were reported in the following departments: Cusco (1 case), Loreto (1) and San Martin (6). All 7 confirmed cases occurred in males.
The age range of all cases was 12?43 years. Seven cases had not been vaccinateded; the vaccination status of the other case was unknown.
Immunization and vaccine coverage in the Region of the Americas
Most countries with enzootic areas in the Region of the Americas introduced yellow fever vaccine into their routine immunization schedules in 2000. Notably, Panama started vaccinating against yellow fever routinely in 1974, and Guyana did so in 1980. As of 2009, 8 countries with enzootic areas had introduced the vaccine into their national immunization schedules for all children at age 1 year, which is the same time that children receive measles?mumps?rubella (MMR) vaccine; these countries are the Plurinational State of Bolivia, the Bolivarian Republic of Venezuela, Colombia, Guyana, Paraguay, Peru, and Trinidad and Tobago. Yellow fever vaccine is administered to children at age 9 months in Brazil and French Guiana; Ecuador, Panama, and Suriname vaccinate in enzootic areas.
Paraguay had introduced vaccination into areas bordering enzootic municipalities in neighbouring countries in 2001; Argentina did so in 2002. In 2007, Paraguay decided to make yellow fever vaccination universal.
Coverage of routine yellow fever vaccination among children has varied over time and by country, but coverage for this vaccine is often lower than coverage for MMR vaccine.
Supplementary vaccination activities have varied among countries, conducted either as campaigns following outbreaks or as preventive campaigns. In 2004, Peru started implementing a plan aimed at vaccinating 11 975 137 people in endemic areas aged 2?59 years and migrants to those areas. By the end of 2008, the country had vaccinated approximately 11 million people, reaching an average coverage rate of 98%, which was verified by rapid monitoring of coverage in all regions included in the national plan.
Following an outbreak in 2008 that extended from Brazil to Paraguay and to northern Argentina, Paraguay conducted a vaccination campaign aimed at people aged >1 year living in an affected area or a surrounding area; a total of 3.5 million people were vaccinated.
Argentina also carried out mass campaigns during the first quarter of 2008; close to 1.4 million people were vaccinated. The increase in yellow fever activity in the Region of the Americas in 2008 led to a worldwide shortage of yellow fever vaccines.
Epizootics in the Region of the Americas
During 2008 and 2009 some countries carried out surveillance of deaths among primates. Their reports led to the confi rmation of several epizootics.
In November 2007 in Argentina, a laboratory confirmed epizootic was identifi ed in Iguazu department, Misiones province. In early January 2008, several dead monkeys were reported in the departments of Apostoles, Capital y Concepci?n, Guaran? and San Pedro, all of which are in Misiones province. Further epizootics were confirmed in this province in October 2008, when 8 dead monkeys were reported near El Soberbio locality, and in December 2008, when 6 dead monkeys were notifi ed in the municipalities of Az?l, Cerro, Garup? and San Jos? in Misiones province.
In Brazil in 2007, intense circulation of the virus in nonhuman primates was identified in the central and southeastern regions of the country; this was followed by the human outbreak of sylvatic yellow fever described earlier.
The epizootic continued to be seen in the same area during 2008.
In Brazil in October 2008, dead monkeys were also reported in the north-western part of Rio Grande do Sul state. Active surveillance has been implemented, and more epizootic areas have been found in places previously considered to be non-enzootic. This finding led national authorities to carry out an extensive vaccination campaign throughout almost all of Rio Grande do Sul.
Circulation of sylvatic yellow fever virus continued throughout 2009 in Brazil, causing more epizootic cases (especially in Rio Grande do Sul state) and human cases.
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