How Global Warming Will Affect Insect-Transmitted Diseases

By Chris Williams on December 31, 2015.

Most of us don’t see how global warming with its rising sea levels and melting ice caps is going to have a significant impact on us, at least in our lifetimes. But a more intimate aspect of global warming is happening now and has the potential to impact us personally. Experts say that a warmer U.S. will mean larger numbers of insect pests and new outbreaks of insect-transmitted diseases. In general, the U.S. is facing shorter and milder winters with fewer hard freezes, allowing infected pests to survive and begin spreading disease earlier in the season than before.

We’re already seen this happening here in the U.S. In 2012, the winter in northern Texas was unusually mild, bringing on droves of spring mosquitoes that were carrying disease. The scenario played out as these mosquitoes continued to multiply during a very warm and muggy May. By mid-June, Dallas had recorded the season’s first case of West Nile virus. By the end of August, there were almost 400 cases, including 19 deaths in the nation’s worst West Nile epidemic. Analysis as to why this happened puts a good part of the blame on consistently warmer temperatures. Not only are insects more active and reproducing faster in warmer weather, but the disease organisms that they carry also replicate faster, setting the scene for a perfect storm.

Tropical Pests Could Make U.S. Their New Home

The range of disease-carrying pests is also changing as more infected tropical pests move northward and into the U.S. where warmer temperatures, at least in southern states, now allow them to survive. As a result, health departments in the south are preparing for mosquito diseases like chikungunya virus and dengue fever, which were rarely seen in the U.S., and a resurgence in Chagas disease spread by a blood-sucking bug.

Robert Haley, Univ. of TX Southwestern Medical Center epidemiologist, said “Climate change is broadening the tropical latitudes…While the widespread return of major killers such as malaria are unlikely in an advanced Western country, you can roughly predict that tropical diseases will be part of our future.”

Here in the Northeast, we have our own concerns about tick-borne diseases, especially Lyme disease. Global warming has allowed disease-carrying ticks to expand their range into now warmer parts of Canada. In our region, milder winters mean larger tick populations surviving to spread disease next spring and summer.

[Source: “A Warming Globe Brings Invisible Threat: Disease,” Joby Warrick. The Washington Post, Nov. 28, 2015.]



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