Posted by: Michael Ritter PhD | September 20, 2007

Dengue Fever Expanding its foothold in Texas

The recent emergence of deadly diseases like Ebola as a threat to humans has been a result of habitat encroachment and climate change. Intact habitats tend to inhibit the spread of infectious agents. Damaged, altered, and degraded habitats trigger the spread of new and existing diseases to humans. A 2005 United Nations Global Environment Outlook Year Book 2004/5 reported that the deadly Nipah virus, normally found in Asian fruit bats, is believed to have passed over to humans. Land clearance for palm plantations brought bats in contact with swine, and then humans as their habitat shrunk.

The geographic range and seasonality of mosquito-borne diseases like malaria are very sensitive to changes in climate. The spread of West Nile Virus has been linked to climate change due to global warming. West Nile outbreaks have been related to a combination of heat and drought followed by heavy downpours of rain. These conditions are likely to occur more often with global warming according to the intergovernmental Panel on Climate Change.

The first documented case in the United States occurred in New York City in 1999. The hot, dry spring created stagnant polluted pools of water, a perfect breeding ground for mosquitoes. Birds drawn to the pools were infected by the mosquitoes. Uninfected birds escaped to wetter habitats as the drought worsened. In the absence of birds, the mosquitos turned to humans for sustenance. In the end, 8,000 people became infected with the virus, 62 had fallen ill and seven people died.

The threat of Dengue fever is increasing along the Mexico-US border and global warming may be causing it. The mosquito species responsible for spreading the virus is now well established in south Texas. A recent outbreak in Brownsville, Texas put 38% of the town at risk for the most dangerous form of the disease, dengue hemorrhagic fever.
See:

TPE Link – Habitat Change and Human Activity

Culex pipiens quinquefasciatus mosquito. Image courtesy USGS

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