Shiloh
Editor, Senior Moderator
Source: http://www.eht-forum.org/news.html?fileId=news100121074749&from=home&id=0
Thursday 21 January 2010
Dengue trends ?worrisome? in the Americas
Researchers track decades of dengue data in the Americas for the first time
he number of reported cases of dengue fever in the Americas has more than quadrupled over the past three decades, say public health officials working in the region this month in the American Journal of Tropical Medicine and Hygiene.
?Since 1980, the disease has broadly expanded throughout the region,? write Jos? Luis San Mart?n and colleagues. Reported cases of the disease continent-wide rose from around 16 per 100,000 people in the 1980s, to more than 70 per 100,000 people between 2000 and 2007.
As spread of the dengue virus picks up speed, they fear a future rise in the number of people suffering from the deadly haemorrhagic form of the disease. This typically affects people infected by the virus repeatedly.
The research published this month already uncovers an ?alarming? increasing trend in cases of dengue haemorrhagic fever. The number of these cases has risen eight-fold since the 1980s, with more serious cases occurring in children than ever before.
Although health officials across the continent believe the incidence of dengue fever is growing, because a higher number of patients are seeking medical care for the disease, until now there has been no comprehensive, evidence-based assessment of disease patterns in the region. Working with dengue infection records held by national health ministries, the World Health Organization and the regional body, the Pan American Health Organization (PAHO), Mart?n and colleagues examined disease patterns on the continent with a dataset that included all reported dengue infections from all countries in the region between 1980 and 2007.
They found that the dengue virus first appeared in the region in 1977, when it was spotted in Jamaica. From there it spread to Cuba, Puerto Rico and Venezuela, and eventually to the rest of the Caribbean countries, Mexico, other parts of Central America, and northern South-American countries. ?During the 80s, dengue started to circulate in Brazil, Bolivia, Paraguay, Ecuador, and other South American countries that had not experienced the disease before,? write the authors.
There are four different strains (or serotypes) of the dengue virus. Over the thirty years since the 1980s, all four serotypes cropped up across the region. Today, dengue is ?hyperendemic? in the Americas, say Mart?n and colleagues ? this means it affects a high proportion of people at risk.
The risk of fatalities rises as new serotypes are introduced to parts of the continent where they never circulated before, they add. Becoming infected with a second serotype of the virus after having recovered from an earlier infection caused by a different serotype increases in the risk of developing dengue haemorrhagic fever.
Several factors could be behind the increase in cases seen over the past few decades, explain Mart?n et al. The number of native Aedes aegypti mosquitoes that carry the dengue virus has increased since the 1970s after a PAHO eradication program ended. A new mosquito species, Aedes albopictus, was reported in the region in 1985 and could be fuelling the rise in cases and rates of dengue fever seen in the region. This mosquito is also capable of carrying the virus, but scientists are still unsure of exactly what role it plays in the spread of the disease.
?In addition, population growth, unplanned urbanisation with poor sanitary conditions, deterioration of the public health infrastructure, and a decreased access to health care has also contributed to the increase of disease burden,? write the authors.
Public health officials have limited tools to control the disease as there is currently no vaccine against it. Keeping check of the mosquitoes that carry the dengue virus is the only way to control the disease. But this strategy is expensive and difficult to maintain.
The authors acknowledge that their research has limitations. The findings are based on data collected through a passive surveillance system, whereby local officials report cases to international authorities as and when they crop up. This type of system usually underestimates the true number of cases, they explain.
Reference and link
1.
Mart?n JLS, Brathwaite O, Zambrano B, Sol?rzano, Bouckenooghe A, Dayan GH, et al. The epidemiology of dengue in the Americas over the last three decades: a worrisome reality. Am J Trop Med Hyg 2010, 82:128?35. doi: 10.4269/ajmh.2010.09-0346
World Health Organization information about dengue fever
Thursday 21 January 2010
Dengue trends ?worrisome? in the Americas
Researchers track decades of dengue data in the Americas for the first time
he number of reported cases of dengue fever in the Americas has more than quadrupled over the past three decades, say public health officials working in the region this month in the American Journal of Tropical Medicine and Hygiene.
?Since 1980, the disease has broadly expanded throughout the region,? write Jos? Luis San Mart?n and colleagues. Reported cases of the disease continent-wide rose from around 16 per 100,000 people in the 1980s, to more than 70 per 100,000 people between 2000 and 2007.
As spread of the dengue virus picks up speed, they fear a future rise in the number of people suffering from the deadly haemorrhagic form of the disease. This typically affects people infected by the virus repeatedly.
The research published this month already uncovers an ?alarming? increasing trend in cases of dengue haemorrhagic fever. The number of these cases has risen eight-fold since the 1980s, with more serious cases occurring in children than ever before.
Although health officials across the continent believe the incidence of dengue fever is growing, because a higher number of patients are seeking medical care for the disease, until now there has been no comprehensive, evidence-based assessment of disease patterns in the region. Working with dengue infection records held by national health ministries, the World Health Organization and the regional body, the Pan American Health Organization (PAHO), Mart?n and colleagues examined disease patterns on the continent with a dataset that included all reported dengue infections from all countries in the region between 1980 and 2007.
They found that the dengue virus first appeared in the region in 1977, when it was spotted in Jamaica. From there it spread to Cuba, Puerto Rico and Venezuela, and eventually to the rest of the Caribbean countries, Mexico, other parts of Central America, and northern South-American countries. ?During the 80s, dengue started to circulate in Brazil, Bolivia, Paraguay, Ecuador, and other South American countries that had not experienced the disease before,? write the authors.
There are four different strains (or serotypes) of the dengue virus. Over the thirty years since the 1980s, all four serotypes cropped up across the region. Today, dengue is ?hyperendemic? in the Americas, say Mart?n and colleagues ? this means it affects a high proportion of people at risk.
The risk of fatalities rises as new serotypes are introduced to parts of the continent where they never circulated before, they add. Becoming infected with a second serotype of the virus after having recovered from an earlier infection caused by a different serotype increases in the risk of developing dengue haemorrhagic fever.
Several factors could be behind the increase in cases seen over the past few decades, explain Mart?n et al. The number of native Aedes aegypti mosquitoes that carry the dengue virus has increased since the 1970s after a PAHO eradication program ended. A new mosquito species, Aedes albopictus, was reported in the region in 1985 and could be fuelling the rise in cases and rates of dengue fever seen in the region. This mosquito is also capable of carrying the virus, but scientists are still unsure of exactly what role it plays in the spread of the disease.
?In addition, population growth, unplanned urbanisation with poor sanitary conditions, deterioration of the public health infrastructure, and a decreased access to health care has also contributed to the increase of disease burden,? write the authors.
Public health officials have limited tools to control the disease as there is currently no vaccine against it. Keeping check of the mosquitoes that carry the dengue virus is the only way to control the disease. But this strategy is expensive and difficult to maintain.
The authors acknowledge that their research has limitations. The findings are based on data collected through a passive surveillance system, whereby local officials report cases to international authorities as and when they crop up. This type of system usually underestimates the true number of cases, they explain.
Reference and link
1.
Mart?n JLS, Brathwaite O, Zambrano B, Sol?rzano, Bouckenooghe A, Dayan GH, et al. The epidemiology of dengue in the Americas over the last three decades: a worrisome reality. Am J Trop Med Hyg 2010, 82:128?35. doi: 10.4269/ajmh.2010.09-0346
World Health Organization information about dengue fever