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[SANTIAGO] Dengue cases in Central and Latin America have increased almost five-fold in incidence in the last 30 years, researchers have found.

There were 4.8 million dengue cases reported to the Pan American Health Organization (PAHO) between 2000 and 2007, compared with 2.7 million in the 1990s and one million in the 1980s.

And the pattern of disease is becoming more severe as children become more vulnerable than adults to the disease — as in South-East Asia. Transmission is now occurring in almost all countries in the region.

Cases of dengue haemorrhagic fever (DHF), a potentially fatal complication, have also increased — from just more than 13,000 cases in the 1980s to more than 100,000 cases between 2000 and 2007.

Although deaths in Central and Latin America have increased from 242 in the 1980s to almost 1,400 between 2000 and 2007, most deaths still occur in South-East Asia and the Western Pacific where DHF rates are higher.

The authors said this may be because the dengue strain associated with DHF in South-East Asia is more virulent than its American equivalent.

"The pattern of dengue in the Americas is changing, becoming more similar to the Asian profile, with more paediatric cases rather than adult cases," said Olivia Braithwaite, a researcher at the PAHO Regional Program on Dengue and co-author of the study.

She told SciDev.Net that this may be because, as adults are exposed to several types of dengue, they develop resistance to the disease.

Dengue is transmitted primarily by Aedes aegypti mosquitoes and mosquito control is the only prevention method.

The collapse of the regional A. aegypti eradication programme in the 1940s — leading to more mosquitoes since the 1970s — could be behind the escalation, said the researchers.

Other possible factors include population growth, unplanned urbanisation with poor sanitary conditions, international travel and climatic changes.

They call for the implementation of PAHO's Integrated Management Strategy for Dengue Prevention and the development of vaccines to protect against the four types of dengue virus.

The most advanced candidate is a three-dose vaccine developed by Sanofi Pasteur.

Phase II clinical studies on adults and children in Latin America and South-East Asia are being carried out, said Jean Lang, associate vice president and dengue programme leader at Sanofi Pasteur. The vaccine should be launched in 2015–16.

The research was published in the January issue of the American Journal of Tropical Medicine and Hygiene.

References

American Journal of Tropical Medicine and Hygiene 82, 128 (2010)

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