Residents Reminded to Take Precautions to Avoid WNV

(GantDaily Graphic)

HARRISBURG – The Pennsylvania Department of Health reminds Pennsylvanians to take precautions to reduce exposure to mosquitoes as the season arrives for West Nile virus, or WNV, infections.

This year, mosquito sampling is showing earlier and more frequent evidence of WNV circulation in Southeastern Pennsylvania than in recent years.

“All Pennsylvanians should take steps to reduce breeding sites for mosquitoes around their homes, and use insect repellants when outdoors,” advised Secretary of Health Everette James. “This is even more important for older citizens and for people with weakened immune systems, who are at greater risk of severe illness if they contract West Nile virus.”

The Pennsylvania Department of Environmental Protection, or DEP, conducts programs to monitor and control mosquito populations around the state. This year, testing has shown that 25 “pools” of mosquitoes trapped through July 9 have evidence of WNV infection, with 20 of these positive mosquito pools collected in Delaware County. The other positive pools were found in Bucks, Lancaster, Montgomery, and Philadelphia counties. As the season progresses, other locations are expected to also see WNV activity.

Although WNV has reappeared every summer in Pennsylvania since first detected 10 years ago, the positive findings in 2010 are earlier — and in greater numbers – than those seen in the last few years, which could indicate that the risk to humans may also be higher this year. 

The mosquitoes that transmit WNV breed in areas with standing and stagnant water. Ideal locations include clogged gutters, discarded tires, poorly maintained swimming pools, flower pots, and other types of plastic containers.

Some simple steps to eliminate standing water around your home include:

• Dispose of tin cans, plastic containers, ceramic pots, discarded tires, or any object on your property that could collect standing water. Drill holes in the bottom of recycling containers left outdoors;
• Have roof gutters cleaned every year, particularly if the leaves from nearby trees have a tendency to clog the drains;
• Turn over plastic wading pools and wheelbarrows when not in use;
• Do not let water stagnate in birdbaths;
• Aerate ornamental pools or stock them with fish;
• Clean and chlorinate swimming pools and remove standing water from pool covers;
• Use landscaping to eliminate standing water that collects on your property; and
• Standing water that cannot be eliminated should be treated with Bti products, which are sold at outdoor supply, home improvement, and other stores. Bti is a naturally occurring bacterium that kills mosquito larvae but is safe for people, pets, aquatic life and plants.

Although mosquitoes can bite at any time of day or night, they are most active at dawn and dusk. When engaged in outdoor activities, people can avoid mosquito bites by properly and consistently using DEET-containing insect repellants and covering exposed skin with lightweight clothing. To keep mosquitoes from entering a home, make sure window and door screens are in place and are in good condition.

For a fact sheet on the West Nile virus, including symptoms, please visit, click on “Diseases and Conditions” and alphabetically locate the fact sheet. For more information about West Nile virus, including current test results for mosquitoes, birds and horses, visit or call 1-800-PA HEALTH.

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