Dengue Fever in South Florida, Vector-Borne Disease and Climate Change

Stegomyia aegypti (formerly Aedes aegypti) mos...

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For the first time since 1934, Key West has seen an outbreak of dengue fever. With 27 confirmed cases in 2009 and 18 as of July this year, dengue returns once again to Key West.

Dengue fever is the world’s most widespread vector-borne disease. A viral disease, dengue is transmitted by urban Aedes (also known by the genus name Stegomyia) mosquitoes. The Aedes mosquitos, especially the species Aedes aegypti, often live in close proximity to humans in tropical urban areas.

This mosquito lays its eggs in containers filled with water, such as bird baths, cisterns and devices used for water collection.

The spread of vector-borne disease, like dengue fever and malaria, are expected to increase as our climate changes, allowing these mosquitos to inhabit areas that were once too cold for them.

The effects of future climate change on the spread of dengue fever are complicated. In areas where temperature and rainfall increase, we are likely to see a greater spread of the disease. But, rates of dengue transmission may actually increase in regions that are projected to become more drought-prone. This is because as drought increases, there will be greater need for water collection devices like rain-barrels, cisterns, bottles and jugs that serve as a breeding ground for dengue mosquito vectors.

By 2085 climate change will put an estimated 3.5 billion people at risk of dengue fever said the United Nations’s Intergovernmental Panel on Climate Change (IPCC) in 2007. Currently, Canada is the only country in the Americas not experiencing a resurge in dengue fever.

There are four strains of dengue fever. When a person contract the disease, he or she develops immunity to the strain of dengue they have contracted, but not to the to the other types of dengue fever. According to the WHO, there is good evidence that the person becomes more apt to contract dengue haemorrhagic fever if infected with another strain of the virus. Dengue haemorrhagic fever is a leading cause of serious illness and death among children in some Asian countries.

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