West Nile Virus


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America sees its Worst West Nile Virus Outbreak so far

While West Nile Virus (WNV) and other mosquito-borne illnesses are not uncommon around the world, they have gained a lot more attention in recent years, as the number of cases and the spread of these diseases has grown substantially. North America has been strongly affected by the West Nile outbreak, with Texas taking the worst of it; cases there have doubled within the past two weeks alone.

Contributing Factors
West Nile OutbreakThis year's West Nile outbreak (2012) is the worst in recent history, with over 1,600 cases and 66 deaths in the United States (see more on the history of West Nile). A number of different factors have lead to this epidemic:

  • Potential virus mutation, indicated by the manifestation of different symptoms with this year's virus, as opposed to previous years
  • Sporadic rains, following a year of drought; hurricane and flood conditions throughout the southeast United States
  • Negligence and apathy in regards to following disease prevention and protection guidelines, including the clearing of standing water.

As opposed to last year's NWV, which manifested with flu-like symptoms, this year's virus seems to have additional neurological effects, making for a more deadly strain for two main reasons. First, without the exhibition of flu-like symptoms, the illness might go unnoticed, allowing it to get further along before treatment is sought. Secondly, an increased occurrence of neurological symptoms means an increased likelihood of meningitis or encephalitis, two of the complications that make West Nile Virus so deadly.

Hurricane Isaac
The Center for Disease Control (CDC) and many communities along the Gulf Coast are on the lookout for a surge in the number of West Nile cases following Hurricane Isaac's landing in Louisiana. Thunderstorms have caused power outages, leaving over 200,000 people homeless--which cripples the ability to defend against mosquito-borne illnesses due to loss of suitable clothing, window screens, insect repellents, and other safety necessities--but this is not the greatest threat posed by the storm.

The biggest challenge that Isaac presents is the simple fact that there is now a seemingly endless extent of standing water-- and not just in Louisiana and Mississippi, where the storm hit hardest, but also from Texas to the eastern seaboard, where the associated thunderstorms have struck. Standing water is ground zero for mosquitoes, an ideal breeding center for insects that lay eggs in warm, stagnant waters, which precisely describes the kind of conditions now prevalent in the southeastern United States. While the CDC is helping to clear out standing water in the areas worst hit, other regions are reporting water depth of five feet; moreover, with a primary levee burst in the area with the most water, there is nowhere for that overflow to go.

Such a disaster could mean that the greatest danger of the hurricane season is yet to come, as hundreds of thousands are left unprotected, and increased mosquito breeding adding up to a recipe guaranteed to worsen the West Nile outbreak. For more information about the damage caused by Hurricane Isaac, see http://www.nydailynews.com/news/national/days-hurricane-isaac-flooding-outages-remain-louisiana-article-1.1150290.

Halting Mosquito Breeding
Mosquitoes, primarily the Culex mosquitoes (although the west coast of the United States has found other species of mosquitoes that carry the virus, the Culex is the primary disease carrier throughout the US), can grow from egg to full-grown adult in as little as 10 days. They are particularly problematic because they can reproduce in even the smallest amount of water, which means that constant vigilance is a must in order to spot and remove standing water sources. While they need relatively still water in which to thrive, they can survive in conditions of moderate agitation, as long as the surface of the water is predominantly calm (fountains that run on timers, for instance, still provide a fertile breeding ground).

Many communities are addressing the mosquito breeding problem by placing mosquito fish (Gambusia affinis) or guppies into freshwater sources, as these types of fish feed on mosquito larvae and thereby can keep a small pool or pond from producing millions of mosquitoes every week. Agitating standing water and skimming the surface will also help to destroy the larvae and eggs, but removing the standing water altogether is the best solution.

WNV Treatments
For a medical look at West Nile Virus in North America, read this article from the USGS National Wildlife Health Center:

While scientists have yet to develop a vaccine for West Nile Virus, researchers at Utah State University have recently made a breakthrough when they discovered the exact part of the brain that WNV affects. With this knowledge, it will be easier to develop treatment options and perhaps a vaccine in the future--not only for West Nile Virus, but potentially for a range of viruses, as the mechanism that causes death is unknown in the vast majority of viral brain diseases.

Whilst the current West Nile outbreak has alarmed a lot of people, there are a number of things that you can do to offset the risks--staying informed is the first step towards keeping this danger at bay!


Irene Gradinger is editor for The West Nile Virus website. For more information about the disease, visit her site at www.west-nile-virus-prevention.com.


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