Annual buzz about West Nile

Consumer Reports News: August 20, 2008 10:36 AM

As it seems to every summer, the buzzing of mosquitoes has turned to media buzz about West Nile virus. The Boston Globe recently reported that West Nile has been "established in Massachusetts for the summer." Last week a newspaper headline in Illinois read "West Nile cases now official in Illinois" announcing the first human case in the state for the year. And we could go on about other regions as well, but the fact is if you live in the continental United States, you should consider your mosquito season to be West Nile virus season. Every state except Alaska and Hawaii has had incidents of the virus reported in humans, or in birds, mosquitoes, or other animals over the past three years.

Take a look at this map of incidents to date this year from the Centers for Disease Control and Prevention (CDC). All but 10 states in the continental United States have already had either human, or avian, mosquito, or other animal cases reported. And mosquito season lasts until the first hard frost. On last year’s CDC map of the 48 contiguous states, only Maine remained free of the virus.

To understand the West Nile threat: The virus, which appeared in North America in 1999, is spread by mosquitoes. The CDC has estimated that there were approximately 175,000 West Nile virus infections last year, but fortunately most of them don’t cause any significant illnesses. About 20 percent of infections lead to West Nile fever, and fewer still cause more serious conditions including meningitis and encephalitis. The CDC reported that there were 124 fatalities from West Nile in 2007.

For those who do get infected, a study released Monday in the Annals of Internal Medicine suggests that there is a pretty good long-term prognosis for non-fatal symptomatic infections. On average, the study concludes, people tend to fully recover from West Nile illnesses in about a year.

While this is certainly good news, prevention is the better tack and it’s relatively easy. It’s particularly important for people over 50 who run a higher risk of developing a severe illness. Here are simple steps you can take to prevent mosquito bites, and therefore, West Nile infections:

  • Protect your home by keeping your yard free of standing water where mosquitoes like to breed, and install screens to keep the pests out of your house.
  • Staying inside from dusk throughout the evening, when mosquitoes are most active, is the best way to prevent bites. But if you're anything like me, sacrificing those summer evenings is out of the question, so use an insect repellent when you venture out. The U.S. Environmental Protection Agency has said that deet-based repellents are safe when used as directed, so read the packaging carefully. We recommend using the lowest concentration that works, especially on kids, and never using deet on infants. Check out our buying advice and latest Ratings of insect repellents this blog post for more on ticks, and read more on how to prevent and treat Lyme disease..

For more on preventing West Nile virus infections see our previous coverage. And mosquitoes aren’t the only summer pests that spread disease. If you live in the East, also take caution with Lyme disease-carrying ticks. See this blog post for more on ticks, and read more on how to prevent and treat Lyme disease.

Kevin McCarthy, associate editor


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