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Reference Desk August 2012

West Nile on the Rise Again After Quiet Decade

    PISCATAWAY, New Jersey, August 18, 2012—This past year’s mild winter and wet spring could be contributing to the worst West Nile virus outbreak since the disease was first detected in the United States in 1999. According to the Centers for Disease Control and Prevention, there have been more cases of the virus so far this year than any year. As of August 14, 2012 almost 700 cases had been reported across the nation, including 26 deaths.

    “Mosquitoes become infected when they feed on infected birds. Normally, the number of mosquitoes decreases greatly during the cold months, with a small proportion of mosquitoes surviving, or ‘overwintering.’ This year, with a mild winter, more mosquitos survived and so we’re seeing a bumper crop,” explains George DiFerdinando Jr., MD, MPH, director of the New Jersey Center for Public Health Preparedness at the University of Medicine and Dentistry of New Jersey.

    West Nile virus is a seasonal epidemic in North America that flares up in the summer and continues into the fall and is spread by the bite of an infected mosquito. The virus is not spread person to person through casual contact.

    People typically develop West Nile symptoms between three and 14 days after being bitten by an infected mosquito. While about 80% of those infected will not exhibit symptoms, 20% have symptoms such as fever, headache and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for as little as a few days, or as long as several weeks, even in people who are otherwise healthy. About one in 150 people infected with West Nile virus will develop severe, potentially fatal, illness. Symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. In these cases, neurological effects may be permanent.

    “Anyone with a compromised immune system is at a higher risk to contract a severe form of the illness,” says DiFerdinando. “This includes those of us over 50, those with diseases such as blood cancers or HIV and people who are taking medicines that weaken the immune system, like prednisone. These people as well as anyone who spends a significant amount of time outdoors should take precautions to avoid mosquito bites.”

    DiFerdinando says you minimize your risk in two ways: Reduce the number of mosquitoes on your property and decrease your direct exposure to mosquitoes. He recommends taking the following precautions:

    • Stay inside at dawn and dusk, the times when mosquitoes are most active.
    • Wear long sleeves and pants or Permethrin-treated clothing.
    • Use EPA-approved insect repellent like DEET, Picaridin, oil of lemon eucalyptus (or its synthetic version, PMD) or IR3535. Spray the repellent on your clothes before you put them on—not directly on your skin—and allow the clothes to dry before putting them on. Shower when you come inside.
    • Get rid of mosquito breeding sites by emptying standing water from flowerpots, buckets and barrels. Change the water in pet dishes and replace the water in birdbaths weekly. Drill holes in tire swings so water drains out. Keep children’s wading pools empty and on their sides when they are not being used.
    • Make sure you have good screens on your windows and doors to keep mosquitoes out.

    Click here for more information and CDC resources on the West Nile virus.

    For more information, see Vetlearn's care guide, West Nile Virus and Your Pet.

    Source: University of Medicine and Dentistry of New Jersey


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