Unusual Heat May Have Boosted West Nile Virus Last Year: CDC

MONDAY May 13, 2013 -- Higher-than-normal temperatures last year may have led to an increase in West Nile virus cases, say U.S. health officials.

More deaths from West Nile virus were reported in 2012 -- 286 in all -- than in any year since 1999, when the mosquito-borne disease was first detected in the United States, the U.S. Centers for Disease Control and Prevention reported Monday. And the total number of cases -- 5,674 -- was the largest on record since 2003.

"Last summer's outbreak likely resulted from many factors, including higher-than-normal temperatures that influenced mosquito and bird abundance, the replication of the virus in its host mosquitoes, and interactions of birds and mosquitoes in hard-hit areas," the CDC stated in an advisory.

Texas accounted for 33 percent of all reported West Nile virus cases in 2012, the agency said. Other states with the greatest concentration of cases were California, Louisiana, Michigan, Mississippi, Oklahoma and South Dakota.

But don't think that if you live elsewhere in the United States that you're safe from West Nile virus. "Because the factors that lead to West Nile virus disease outbreaks are complex, CDC cannot predict where and when they will occur," the agency said in the advisory.

More than half of all 2012 cases were classified as neuroinvasive disease, meaning they resulted in serious illness such as meningitis or encephalitis.

"Last year's large outbreak is a reminder that it is important for people to protect themselves from West Nile virus, especially as we head into summer and mosquitoes become more active," the CDC said. "The best way to prevent West Nile virus disease is to avoid mosquito bites."

The agency offered these prevention tips:

  • Use insect repellents when you go outdoors. Look for repellents containing DEET, picaridin, IR3535, and para-menthane-diol (PMD) because they provide longer-lasting protection than other products.
  • Wear long sleeves and pants at dawn and dusk when many mosquitoes are most active.
  • Repair or install screens on doors and windows. Use air conditioning, if you have it.
  • To help keep mosquitoes away from your home, empty sources of standing water such as flowerpots, gutters, buckets and kiddie pools. Change birdbaths weekly.

The symptoms of West Nile virus include fever, headache, body aches, skin rash and swollen lymph glands. They can last just a few days or several weeks, and usually go away on their own, the CDC said.

More information

The U.S. National Library of Medicine has more about West Nile virus.

Posted: May 2013


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