Dawn of the Spread (of dengue virus vectors)

A paper published today in the journal eLIFE describes work to model the distribution of two species of mosquito, Aedes aegypti (yellow fever mosquito) and Aedes albopictus (Asian tiger mosquito). These two species are vectors of dengue, yellow fever, and chikungunya viruses; their presence may precede autochthonous cases of these diseases. The model developed by these researchers is based on recorded occurrences of mosquitoes, their eggs or larvae (the largest number of records of this type ever compiled) and environmental factors including temperature and type of land cover.

Aedes aegypti” by James Gathany – CDC

The model predicts that these two vectors are spreading throughout the world, and are present on all continents. The authors hypothesise  that where the vectors are, the virus and disease might follow.

Existing research has already documented that cases of dengue fever are appearing in new geographic regions. With an increasing geographical spread of vector and virus we can expect an increase in the incidence and disease burden of dengue fever. Dengue fever is one of the better funded neglected tropical diseases, but there is not yet any treatment or vaccine licensed for use. Treatment is supportive only, and consists of rehydration and sometimes blood transfusion. There is hope of a vaccine, one tested in phase III clinical trials in Asia and Latin America in 2014 has shown mixed results.

However, the threat of spreading vectors and increasing cases of dengue fever in Europe are not the only reasons we might be interested in tackling this disease.

Currently, dengue virus causes 100 million apparent infections each year and is a leading cause of serious illness and death in children in some Asian and Latin American countries. Common symptoms include fever, headache, muscle and joint pain, and skin rashes, and the disease can progress to dengue haemorrhagic fever, with bleeding, low platelets, plasma leakage and low blood pressure. Within the last few months outbreaks and high numbers of cases of dengue fever have been reported from many countries including; Yemen, Kuala Lumpur, India, Cambodia, Malaysia, Thailand and Brazil. In countries where a stable and comprehensive health system is not in place, it will be very difficult or impossible to contain outbreaks without international help.

Aedes albopictus” by James Gathany, CDC

This research has mapped the global distribution of dengue virus vector, which is essential for public health planning. If we know where and in what numbers we might encounter cases of dengue fever we are more likely to succeed in preventing and containing outbreaks. Long-term investment in health systems and research will be key in controlling, preventing, treating, and eventually eradicating this disease.

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