Giuseppe
Emeritus
New influenza A(H1N1) virus infections: global surveillance summary, May 2009 (World Health Organization, Weekly Epidemiological Record, vol. 84, n. 20, Edited)
From Weekly Epidemiological Record (WER), May 15, 2009, vol. 84, n. 20, pp 173-184.
[Original Text: LINK - EDITED.]
New influenza A(H1N1) virus infections: global surveillance summary, May 2009
In mid-March 2009, the Ministry of Health of Mexico began to identify an unusual increase in the number of cases of influenza-like illness at a time when seasonal outbreaks are typically declining.1 By mid-April, atypical cases and clusters of severe pneumonia were occurring mainly among previously healthy young adults in different areas of Mexico. Enhanced surveillance
was initiated throughout the country in response.
In late March 2009, 2 children living in adjacent counties in southern California (USA) had onset of acute febrile respiratory illness.2 Clinical specimens collected from both children were tested at local laboratories and identified as influenza A virus. However, since no specific subtype could be identified, the specimens were sent to reference laboratories for further testing. On 15 and 17 April 2009, the United States Centers for Disease Control and Prevention (CDC) determined that these 2 children were infected with a new influenza A(H1N1) virus that contained genetic
material suggestive of swine origin. However, the virus had not been previously detected in pigs or humans.2 Neither of the children had been exposed to pigs or had contact with each other. On 17 April 2009, the United States government alerted WHO about these cases as required under the International Health Regulations (2005). By 24 April 2009, 6 additional cases had been reported from California and Texas (USA).3
On 23 April 2009, the National Microbiology Laboratory of the Public Health Agency of Canada identified the new influenza A(H1N1) virus in samples sent by the Government of Mexico. These viruses were found to be genetically identical to the influenza A(H1N1) viruses from California.4 The Ministry of Health of Mexico immediately reported this information to WHO. On 25 April 2009, having considered the advice of the Emergency Committee convened under the International Health Regulations (2005), the WHO Director-General determined that the situation constituted ?a public health emergency of international concern?. WHO Member States and partners were advised to scale-up their surveillance and epidemic preparedness activities.
On 27 April 2009, after considering the available data on confirmed outbreaks of influenza A(H1N1) in Canada, Mexico and the United States, WHO raised the level of pandemic influenza alert from phase 3 to phase 4.5 Given the widespread circulation of the virus, WHO considered that containment of the outbreak was not possible and recommended that countries focus on mitigation measures.
The Organization did not recommend border closures or restrictions on international travel.
On 29 April 2009, upon evidence of sustained human-to-human transmission in at least 2 countries in 1 region, WHO raised the pandemic alert level from phase 4 to phase 5.5 All countries were advised to be on high alert for unusual outbreaks of influenza-like illness and severe pneumonia; and to enhance their surveillance activities for the early detection of suspected cases, to
implement appropriate case management strategies and to strengthen infection control measures in health facilities.
This report summarizes the global situation of surveillance for new influenza A(H1N1) virus infections as of 12 May 2009.
Epidemiological surveillance*
As of 12 May 2009, 30 countries had officially reported to WHO a total of 5251 confirmed cases of influenza A(H1N1) virus infection (Fig. 1). Of these cases, 5030 (95.8%) were reported from the Region of the Americas, 204 (3.9%) from the European Region and 17 (0.3%) from the Western Pacific Region (Map 1). No confirmed cases were reported from the other 3 WHO regions. Countries reporting the largest number of confirmed cases include the United States (2600), Mexico (2059), Canada (330), Spain (95) and the United Kingdom (55). Together, these 5 countries account
for 4292 (97.9%) of the total confirmed cases. A total of 61 deaths related to infection with influenza A(H1N1) virus have been reported from 4 countries: Mexico (56), the United States (3), Canada (1) and Costa Rica (1).
Region of the Americas
Mexico
The first confirmed case in Mexico had onset of illness on 10 March 2009. Since then, confirmed cases have been reported from 28 of 31 states and the Federal District. Of the confirmed cases, 72.2% were aged <30 years and 1.9% were aged ≥60 years (Fig. 2). Of the laboratory-confirmed cases who died, 40 (71.4%) were aged <45 years and 33 (58.9%) were aged 15?44 years.
United States
The first confirmed case in the United States was reported on 15 April 2009. Since then, confirmed cases have been reported from 43 of 50 states. Of the confirmed cases with known ages, 84.1% were <30 years and 1.5% were ≥60 years (Fig. 2).
Canada
The first confirmed case in Canada had onset of illness on 10 April 2009. Since then, 9 of 13 provinces have reported confirmed cases, with a median age of 22 years. A total of 4 patients were hospitalized and 1 confirmed case has died.
European Region
The European Region has reported a total of 204 confirmed cases from 15 countries, mostly from Spain (95) and the United Kingdom (55). All cases reportedly had mild disease. Several cases were hospitalized, however, primarily for infection control purposes. No deaths have been reported. Detailed information is available for 129 of these confirmed cases. The median age was 23 years, with a range from 3 to 58 years. Most confirmed cases had travelled to areas with known influenza A(H1N1) virus transmission; 21 cases were infected locally through school or household contacts with a confirmed case (10 in the United Kingdom, 9 in Spain and 2 in Germany). In the United Kingdom, 7 of 10 locally acquired infections occurred within a school setting. To date, there has been no sustained community transmission documented.
Western Pacific Region
The Western Pacific Region has reported a total of 17 confirmed cases from 5 countries: Australia (1), China (2), Japan (4), New Zealand (7) and the Republic of Korea (3). Disease was mild in all cases, and no deaths have been reported. Of 10 cases for whom detailed information was available, 9 reported travel to areas with known H1N1 transmission and 1 case acquired infection locally
through a contact with a returning ill traveller.
Clinical illness and transmissibility
Available information to date indicates that most cases of H1N1 infection had typical influenza-like illness with fever, cough, rhinitis, headache and malaise.6 Some laboratory-confirmed cases, however, did not have fever. This suggests that mild and sub-clinical infections can occur with the new H1N1 virus, similar to what is observed for seasonal influenza.
Severe illness and deaths have occurred in Canada, Costa Rica, Mexico and the United States. Detailed clinical information has been reported for 642 laboratory-confirmed cases in the United States.7 The frequency of fever and respiratory symptoms was generally similar among patients in Mexico and the United States.6, 8 However, in contrast to the Mexican experience, 25% of 323 patients in the United States had diarrhoea and 25% of 295 patients had vomiting. Diarrhoea has also been reported among confirmed cases in other countries.6
Of the 399 confirmed cases in the United States for whom hospitalization information was available, 36 (9%) required hospitalization. Of the 22 hospitalized patients for whom more detailed information was available, 12 had factors associated with an increased risk of complications for seasonal influenza, including a chronic medical condition, pregnancy or an age <5 years.7
A primary reason for hospitalization was severe respiratory illness and not for an underlying medical condition. Some patients in Mexico and the United States required mechanical ventilation.6
The virus appears to be easily transmissible from humans to humans. In the United States and Mexico, community transmission has been widespread. Based on limited data, the secondary attack rate is estimated to be about 22%.6 Higher clinical attack rates have been found in selected investigations such as in a school-associated outbreak in New York City; 659 (33%) of 1996 students who responded to a survey reported fever and either cough or sore throat.9 In contrast, 23 (11%) of 210 school staff members reported these symptoms. Preliminary data suggest varying estimates for an incubation period, ranging between 1?5 days (Spain), 4?6 days (United Kingdom) and 2?7 days (United States).6
Analysis of viral isolates
The new influenza A(H1N1) virus has not been identified previously in any species. It is currently believed to be a further genetic reassortant of a triple reassortant swine virus that has been circulating in swine in North America for at least 10 years. This novel virus differs from the original virus in that the neuraminidase and matrix genes have now been replaced by genes from viruses whose apparent closest relatives are swine viruses that were isolated in Europe and Asia.7 The lack of historical data and insufficient geographical coverage of data from swine populations globally limit the ability to make conclusions about where and when this virus emerged.
The specific genetic changes enabling the new influenza A(H1N1) virus to be transmitted among humans remain unknown at this time. Moreover, there is no evidence that the human pathogenicity markers described in previous pandemic viruses, or those from the zoonotic highly pathogenic avian influenza H5N1 virus, are present. The virus appears sensitive to oseltamivir
(Tamiflu) and zanamivir (Relenza), although a genetic mutation conferring resistance to the adamantane class of antivirals is present.7
Editorial note.
Since its initial detection in Mexico and the United States, the new influenza A(H1N1) virus has continued to spread globally. At this time, travel-related cases are being reported from several countries in multiple regions. However, it remains uncertain how fast the virus will spread and whether it will become widely established. Early estimates of epidemiological parameters such as incubation period and attack rates have been derived from a limited number of settings such as households and schools.6 These estimates require further confirmation and assessment in other settings. Although data are limited, an initial characterization of some of the epidemiological and clinical features of the new H1N1 virus is beginning to emerge. In contrast to seasonal influenza disease patterns, children and young adults appear to be disproportionately affected, while older adults are under-represented, especially with regard to severe illness. An analysis of hospitalized cases in the United States and Mexico is remarkable in that few were adults aged ≥60 years, suggesting a dissimilar pattern to that of seasonal influenza.7 The reasons for this are not known at present.
This discrepancy may reflect, in part, a bias in case-ascertainment due to age-specific patterns of travel or the occurrence of school-associated outbreaks in several countries. Since the outbreak is at an early stage, there may not have been adequate time for the virus to spread into older age groups. Older people are more likely to have had prior infection with, or vaccination against, other H1N1 viruses. At this time, there is insufficient laboratory or clinical evidence to determine whether seasonal vaccination confers protection against infection or complications caused by the new H1N1 virus. Further investigation is required.
A spectrum of illness similar to seasonal influenza has been observed for the new influenza A(H1N1) virus. It ranges from a mild illness to more severe disease leading to hospitalization and death in a small proportion of confirmed cases. Among those with self-limited disease, the predominant clinical picture appears to be an uncomplicated influenza-like illness not requiring antiviral treatment. Severe illness has been reported, both in people with and without risk factors for complications of seasonal influenza.
It is notable that a substantial proportion of cases with severe disease occurred among young and healthy adults. In contrast, the vast majority of deaths associated with seasonal influenza occur among the elderly. Most of the clinical complications associated with H1N1 infection, in both healthy individuals and those with underlying medical conditions, appear to be related to severe respiratory disease.
It is important to note that most countries are at an early stage of disease spread and have reported a small number of cases. The experience of Mexico and the United States may indicate that only as more cases occur and as infection spreads into the wider community can a more complete picture of the epidemiological and clinical characteristics of the H1N1 virus begin to be
delineated. Also, different patterns of morbidity and mortality may emerge as the virus spreads globally and affects low-resourced countries and populations disproportionately affected by malnutrition, poor living conditions and other infectious diseases. For example, if studies determine that the virus is shed in the faeces, it could have implications for countries or settings with
inadequate sanitation.
The situation is expected to evolve over time. Countries should remain vigilant for unusual outbreaks of influenza-like illness that could signal the arrival of, or further spread of, the new H1N1 virus. WHO has developed guidance on treatment, infection control and other control measures for the new influenza A(H1N1) virus.10
WHO does not recommend travel restrictions related to the outbreak of the new influenza A(H1N1) virus. However, individuals who are ill should delay their travel plans, and returning travellers who become ill should seek appropriate medical care. These recommendations are prudent measures intended to limit the spread of many infectious diseases, including influenza. Further information on the evolving situation will be available from the WHO web site11 and the Weekly Epidemiological Record.12
1 WHO Department of Epidemic and Pandemic Alert and Response. WHO ad hoc scientific teleconference on the current influenza A(H1N1) situation (available at http://www.who.int/
csr/resources/publications/swineflu/tc_report_2009_04_29/en/index.html; accessed May 2009).
2 Swine influenza A (H1N1) infection in two children, Southern California, March?April 2009. Morbidity and Mortality Weekly Report, 2009, 58(Dispatch):1?3 (available at http://www.cdc.
gov/mmwr/preview/mmwrhtml/mm58d0421a1.htm; accessed May 2009).
3 Update: swine influenza A (H1N1) infections, California and Texas, April 2009. Morbidity and Mortality Weekly Report, 2009, 58(Dispatch):1?3 (available at http://www.cdc.gov/mmwr/preview/
mmwrhtml/mm58d0424a1.htm; accessed May 2009).
4 See http://www.who.int/csr/don/2009_04_24/en/index.html
5 See http://www.who.int/csr/disease/avian_influenza/phase/en/
* Reported by: Ministry of Health of Mexico, Public Health Agency of Canada, United States Centers for Disease Control and Prevention, Health Protection Agency of the United Kingdom, Ministry of Health of Spain, Pan American Health Organization, World Health Organization.
6 WHO Department of Epidemic and Pandemic Alert and Response. WHO Technical Consultation on the severity of disease caused by the new influenza A (H1N1) virus infections (available at http://www.who.int/csr/resources/pu...hnical_consultation_2009_05_06/en/index.html; accessed May 2009).
7 Emergence of a novel swine-origin influenza A (H1N1) virus in humans. New England Journal of Medicine, 2009, 360(19):1?16 (available at http://content.nejm.org/cgi/reprint/NEJMoa0903810.pdf; accessed May 2009).
8 Update: novel influenza A (H1N1) virus infections, worldwide, May 6, 2009. Morbidity and Mortality Weekly Report, 2009, 58(17):453?458 (available at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5817a1.htm; accessed May 2009).
9 See http://www.nyc.gov/html/doh/downloads/pdf/cd/h1n1_stfrancis_survey.pdf
10 See http://www.who.int/csr/resources/publications/swineflu/en/index.html
11 See http://www.who.int/en/
12 See http://www.who.int/wer/en/
<table style="width: auto;"><tbody><tr><td>
</td></tr><tr><td style="font-family: arial,sans-serif; font-size: 11px; text-align: right;">From TABLES</td></tr></tbody></table>
<table style="width: auto;"><tbody><tr><td>
</td></tr><tr><td style="font-family: arial,sans-serif; font-size: 11px; text-align: right;">From TABLES</td></tr></tbody></table>
-
------
From Weekly Epidemiological Record (WER), May 15, 2009, vol. 84, n. 20, pp 173-184.
[Original Text: LINK - EDITED.]
New influenza A(H1N1) virus infections: global surveillance summary, May 2009
In mid-March 2009, the Ministry of Health of Mexico began to identify an unusual increase in the number of cases of influenza-like illness at a time when seasonal outbreaks are typically declining.1 By mid-April, atypical cases and clusters of severe pneumonia were occurring mainly among previously healthy young adults in different areas of Mexico. Enhanced surveillance
was initiated throughout the country in response.
In late March 2009, 2 children living in adjacent counties in southern California (USA) had onset of acute febrile respiratory illness.2 Clinical specimens collected from both children were tested at local laboratories and identified as influenza A virus. However, since no specific subtype could be identified, the specimens were sent to reference laboratories for further testing. On 15 and 17 April 2009, the United States Centers for Disease Control and Prevention (CDC) determined that these 2 children were infected with a new influenza A(H1N1) virus that contained genetic
material suggestive of swine origin. However, the virus had not been previously detected in pigs or humans.2 Neither of the children had been exposed to pigs or had contact with each other. On 17 April 2009, the United States government alerted WHO about these cases as required under the International Health Regulations (2005). By 24 April 2009, 6 additional cases had been reported from California and Texas (USA).3
On 23 April 2009, the National Microbiology Laboratory of the Public Health Agency of Canada identified the new influenza A(H1N1) virus in samples sent by the Government of Mexico. These viruses were found to be genetically identical to the influenza A(H1N1) viruses from California.4 The Ministry of Health of Mexico immediately reported this information to WHO. On 25 April 2009, having considered the advice of the Emergency Committee convened under the International Health Regulations (2005), the WHO Director-General determined that the situation constituted ?a public health emergency of international concern?. WHO Member States and partners were advised to scale-up their surveillance and epidemic preparedness activities.
On 27 April 2009, after considering the available data on confirmed outbreaks of influenza A(H1N1) in Canada, Mexico and the United States, WHO raised the level of pandemic influenza alert from phase 3 to phase 4.5 Given the widespread circulation of the virus, WHO considered that containment of the outbreak was not possible and recommended that countries focus on mitigation measures.
The Organization did not recommend border closures or restrictions on international travel.
On 29 April 2009, upon evidence of sustained human-to-human transmission in at least 2 countries in 1 region, WHO raised the pandemic alert level from phase 4 to phase 5.5 All countries were advised to be on high alert for unusual outbreaks of influenza-like illness and severe pneumonia; and to enhance their surveillance activities for the early detection of suspected cases, to
implement appropriate case management strategies and to strengthen infection control measures in health facilities.
This report summarizes the global situation of surveillance for new influenza A(H1N1) virus infections as of 12 May 2009.
Epidemiological surveillance*
As of 12 May 2009, 30 countries had officially reported to WHO a total of 5251 confirmed cases of influenza A(H1N1) virus infection (Fig. 1). Of these cases, 5030 (95.8%) were reported from the Region of the Americas, 204 (3.9%) from the European Region and 17 (0.3%) from the Western Pacific Region (Map 1). No confirmed cases were reported from the other 3 WHO regions. Countries reporting the largest number of confirmed cases include the United States (2600), Mexico (2059), Canada (330), Spain (95) and the United Kingdom (55). Together, these 5 countries account
for 4292 (97.9%) of the total confirmed cases. A total of 61 deaths related to infection with influenza A(H1N1) virus have been reported from 4 countries: Mexico (56), the United States (3), Canada (1) and Costa Rica (1).
Region of the Americas
Mexico
The first confirmed case in Mexico had onset of illness on 10 March 2009. Since then, confirmed cases have been reported from 28 of 31 states and the Federal District. Of the confirmed cases, 72.2% were aged <30 years and 1.9% were aged ≥60 years (Fig. 2). Of the laboratory-confirmed cases who died, 40 (71.4%) were aged <45 years and 33 (58.9%) were aged 15?44 years.
United States
The first confirmed case in the United States was reported on 15 April 2009. Since then, confirmed cases have been reported from 43 of 50 states. Of the confirmed cases with known ages, 84.1% were <30 years and 1.5% were ≥60 years (Fig. 2).
Canada
The first confirmed case in Canada had onset of illness on 10 April 2009. Since then, 9 of 13 provinces have reported confirmed cases, with a median age of 22 years. A total of 4 patients were hospitalized and 1 confirmed case has died.
European Region
The European Region has reported a total of 204 confirmed cases from 15 countries, mostly from Spain (95) and the United Kingdom (55). All cases reportedly had mild disease. Several cases were hospitalized, however, primarily for infection control purposes. No deaths have been reported. Detailed information is available for 129 of these confirmed cases. The median age was 23 years, with a range from 3 to 58 years. Most confirmed cases had travelled to areas with known influenza A(H1N1) virus transmission; 21 cases were infected locally through school or household contacts with a confirmed case (10 in the United Kingdom, 9 in Spain and 2 in Germany). In the United Kingdom, 7 of 10 locally acquired infections occurred within a school setting. To date, there has been no sustained community transmission documented.
Western Pacific Region
The Western Pacific Region has reported a total of 17 confirmed cases from 5 countries: Australia (1), China (2), Japan (4), New Zealand (7) and the Republic of Korea (3). Disease was mild in all cases, and no deaths have been reported. Of 10 cases for whom detailed information was available, 9 reported travel to areas with known H1N1 transmission and 1 case acquired infection locally
through a contact with a returning ill traveller.
Clinical illness and transmissibility
Available information to date indicates that most cases of H1N1 infection had typical influenza-like illness with fever, cough, rhinitis, headache and malaise.6 Some laboratory-confirmed cases, however, did not have fever. This suggests that mild and sub-clinical infections can occur with the new H1N1 virus, similar to what is observed for seasonal influenza.
Severe illness and deaths have occurred in Canada, Costa Rica, Mexico and the United States. Detailed clinical information has been reported for 642 laboratory-confirmed cases in the United States.7 The frequency of fever and respiratory symptoms was generally similar among patients in Mexico and the United States.6, 8 However, in contrast to the Mexican experience, 25% of 323 patients in the United States had diarrhoea and 25% of 295 patients had vomiting. Diarrhoea has also been reported among confirmed cases in other countries.6
Of the 399 confirmed cases in the United States for whom hospitalization information was available, 36 (9%) required hospitalization. Of the 22 hospitalized patients for whom more detailed information was available, 12 had factors associated with an increased risk of complications for seasonal influenza, including a chronic medical condition, pregnancy or an age <5 years.7
A primary reason for hospitalization was severe respiratory illness and not for an underlying medical condition. Some patients in Mexico and the United States required mechanical ventilation.6
The virus appears to be easily transmissible from humans to humans. In the United States and Mexico, community transmission has been widespread. Based on limited data, the secondary attack rate is estimated to be about 22%.6 Higher clinical attack rates have been found in selected investigations such as in a school-associated outbreak in New York City; 659 (33%) of 1996 students who responded to a survey reported fever and either cough or sore throat.9 In contrast, 23 (11%) of 210 school staff members reported these symptoms. Preliminary data suggest varying estimates for an incubation period, ranging between 1?5 days (Spain), 4?6 days (United Kingdom) and 2?7 days (United States).6
Analysis of viral isolates
The new influenza A(H1N1) virus has not been identified previously in any species. It is currently believed to be a further genetic reassortant of a triple reassortant swine virus that has been circulating in swine in North America for at least 10 years. This novel virus differs from the original virus in that the neuraminidase and matrix genes have now been replaced by genes from viruses whose apparent closest relatives are swine viruses that were isolated in Europe and Asia.7 The lack of historical data and insufficient geographical coverage of data from swine populations globally limit the ability to make conclusions about where and when this virus emerged.
The specific genetic changes enabling the new influenza A(H1N1) virus to be transmitted among humans remain unknown at this time. Moreover, there is no evidence that the human pathogenicity markers described in previous pandemic viruses, or those from the zoonotic highly pathogenic avian influenza H5N1 virus, are present. The virus appears sensitive to oseltamivir
(Tamiflu) and zanamivir (Relenza), although a genetic mutation conferring resistance to the adamantane class of antivirals is present.7
Editorial note.
Since its initial detection in Mexico and the United States, the new influenza A(H1N1) virus has continued to spread globally. At this time, travel-related cases are being reported from several countries in multiple regions. However, it remains uncertain how fast the virus will spread and whether it will become widely established. Early estimates of epidemiological parameters such as incubation period and attack rates have been derived from a limited number of settings such as households and schools.6 These estimates require further confirmation and assessment in other settings. Although data are limited, an initial characterization of some of the epidemiological and clinical features of the new H1N1 virus is beginning to emerge. In contrast to seasonal influenza disease patterns, children and young adults appear to be disproportionately affected, while older adults are under-represented, especially with regard to severe illness. An analysis of hospitalized cases in the United States and Mexico is remarkable in that few were adults aged ≥60 years, suggesting a dissimilar pattern to that of seasonal influenza.7 The reasons for this are not known at present.
This discrepancy may reflect, in part, a bias in case-ascertainment due to age-specific patterns of travel or the occurrence of school-associated outbreaks in several countries. Since the outbreak is at an early stage, there may not have been adequate time for the virus to spread into older age groups. Older people are more likely to have had prior infection with, or vaccination against, other H1N1 viruses. At this time, there is insufficient laboratory or clinical evidence to determine whether seasonal vaccination confers protection against infection or complications caused by the new H1N1 virus. Further investigation is required.
A spectrum of illness similar to seasonal influenza has been observed for the new influenza A(H1N1) virus. It ranges from a mild illness to more severe disease leading to hospitalization and death in a small proportion of confirmed cases. Among those with self-limited disease, the predominant clinical picture appears to be an uncomplicated influenza-like illness not requiring antiviral treatment. Severe illness has been reported, both in people with and without risk factors for complications of seasonal influenza.
It is notable that a substantial proportion of cases with severe disease occurred among young and healthy adults. In contrast, the vast majority of deaths associated with seasonal influenza occur among the elderly. Most of the clinical complications associated with H1N1 infection, in both healthy individuals and those with underlying medical conditions, appear to be related to severe respiratory disease.
It is important to note that most countries are at an early stage of disease spread and have reported a small number of cases. The experience of Mexico and the United States may indicate that only as more cases occur and as infection spreads into the wider community can a more complete picture of the epidemiological and clinical characteristics of the H1N1 virus begin to be
delineated. Also, different patterns of morbidity and mortality may emerge as the virus spreads globally and affects low-resourced countries and populations disproportionately affected by malnutrition, poor living conditions and other infectious diseases. For example, if studies determine that the virus is shed in the faeces, it could have implications for countries or settings with
inadequate sanitation.
The situation is expected to evolve over time. Countries should remain vigilant for unusual outbreaks of influenza-like illness that could signal the arrival of, or further spread of, the new H1N1 virus. WHO has developed guidance on treatment, infection control and other control measures for the new influenza A(H1N1) virus.10
WHO does not recommend travel restrictions related to the outbreak of the new influenza A(H1N1) virus. However, individuals who are ill should delay their travel plans, and returning travellers who become ill should seek appropriate medical care. These recommendations are prudent measures intended to limit the spread of many infectious diseases, including influenza. Further information on the evolving situation will be available from the WHO web site11 and the Weekly Epidemiological Record.12
1 WHO Department of Epidemic and Pandemic Alert and Response. WHO ad hoc scientific teleconference on the current influenza A(H1N1) situation (available at http://www.who.int/
csr/resources/publications/swineflu/tc_report_2009_04_29/en/index.html; accessed May 2009).
2 Swine influenza A (H1N1) infection in two children, Southern California, March?April 2009. Morbidity and Mortality Weekly Report, 2009, 58(Dispatch):1?3 (available at http://www.cdc.
gov/mmwr/preview/mmwrhtml/mm58d0421a1.htm; accessed May 2009).
3 Update: swine influenza A (H1N1) infections, California and Texas, April 2009. Morbidity and Mortality Weekly Report, 2009, 58(Dispatch):1?3 (available at http://www.cdc.gov/mmwr/preview/
mmwrhtml/mm58d0424a1.htm; accessed May 2009).
4 See http://www.who.int/csr/don/2009_04_24/en/index.html
5 See http://www.who.int/csr/disease/avian_influenza/phase/en/
* Reported by: Ministry of Health of Mexico, Public Health Agency of Canada, United States Centers for Disease Control and Prevention, Health Protection Agency of the United Kingdom, Ministry of Health of Spain, Pan American Health Organization, World Health Organization.
6 WHO Department of Epidemic and Pandemic Alert and Response. WHO Technical Consultation on the severity of disease caused by the new influenza A (H1N1) virus infections (available at http://www.who.int/csr/resources/pu...hnical_consultation_2009_05_06/en/index.html; accessed May 2009).
7 Emergence of a novel swine-origin influenza A (H1N1) virus in humans. New England Journal of Medicine, 2009, 360(19):1?16 (available at http://content.nejm.org/cgi/reprint/NEJMoa0903810.pdf; accessed May 2009).
8 Update: novel influenza A (H1N1) virus infections, worldwide, May 6, 2009. Morbidity and Mortality Weekly Report, 2009, 58(17):453?458 (available at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5817a1.htm; accessed May 2009).
9 See http://www.nyc.gov/html/doh/downloads/pdf/cd/h1n1_stfrancis_survey.pdf
10 See http://www.who.int/csr/resources/publications/swineflu/en/index.html
11 See http://www.who.int/en/
12 See http://www.who.int/wer/en/
<table style="width: auto;"><tbody><tr><td>
</td></tr><tr><td style="font-family: arial,sans-serif; font-size: 11px; text-align: right;">From TABLES</td></tr></tbody></table><table style="width: auto;"><tbody><tr><td>
</td></tr><tr><td style="font-family: arial,sans-serif; font-size: 11px; text-align: right;">From TABLES</td></tr></tbody></table>-
------