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West Nile Virus a Nationwide Problem This Year

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While Pennsylvania is on a record pace for West Nile Virus positives this year,   it is hardly alone and not even among the states with the highest numbers. The virus has been found in 48 states,  with Hawaii and Alaska as the only exceptions. 44 states have reported human cases. Over 70% of those cases are in six states; Texas, South Dakota, Mississippi, Oklahoma, Michigan and Louisiana.

Dr. Lyle Petersen, Director of the CDC’s Division of Vector Borne Infectious Diseases, says the number of human cases rose 25% in the last week, but it appears the epidemic may have peaked in August. He adds a great number of cases may still be reported because it can take 3 to 14 days for symptoms to appear.

Pennsylvania has had 16 human cases reported through September 6th, 11 of them were the more serious neuro-invasive form on the disease.  One of the victims died.  There have been 18 veterinary cases, mostly in horses. 103 dead birds have tested positive, including six Great Horned Owls, two American Kestrels and 11 hawks (Red tail, Cooper’s, Broad-winged and Sharp-shinned). The state has recorded 29 hundred positive mosquitoes.

With the recent heavy rains in some areas, people are advised to eliminate standing water around their homes.  The common house mosquito is one of the carriers of the virus and usually doesn’t stray far from where it breeds.  It can breed in about an inch of water. The rain may have washed away a number of larvae, but it will also create more breeding ground for the mosquitoes to reproduce.

West Nile Virus Present in 47 States

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It’s shaping up to be a bad year for West Nile Virus in the United States, with 47 states reporting positive samples and 38, including Pennsylvania, reporting human cases.

Texas is the hardest hit with about half of the 11 hundred human cases.  Pennsylvania has 8 so far.  Dr. Lyle Petersen, director of the CDC’s Division of Vector Borne Infectious Disease, says the mild winter, early spring and hot summer may be factors. More than half of the human cases have been the more serious neuro-invasive disease, including five of Pennsylvania’s cases.

The human cases in Pennsylvania have occurred in Delaware (2), Bucks, Centre, Franklin, Lancaster, Lebanon and Lehigh Counties.  The state has three blood donor samples testing positive for the presence of the virus.  There have been 7 positive veterinary samples, mostly involving horses and nearly 24 hundred positive mosquito samples.

The CDC is reminding people to take precautions against mosquito bites and take steps around their homes to eliminate standing water that can serve as breeding grounds for mosquitoes.

Dr. Petersen says it takes 3 to 14 days for symptoms to appear, meaning the cases reported now reflect infections from a week or more ago.  He says they expect many more cases to be reported and the risk of infection will continue through the end of September.

More Human Cases of West Nile Virus Confirmed in Pennsylvania

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The state’s West Nile Virus count stands at five with three more confirmed cases added this week.   The new cases involve two men in Delaware County and a woman in Centre County.  The earlier cases were in Franklin and Lancaster Counties.  Both were women.

Amanda Witman, spokeswoman for the Pennsylvania Department of Environmental Protection, says more than 18 hundred mosquitoes have tested positive for the virus, which is a very high infection rate.  She says Pennsylvania is on track to exceed the highest year ever.

DEP is asking people to eliminate standing water around their homes to reduce mosquito breeding grounds. Witman says it only takes a teaspoon of water for a mosquito to begin breeding and some areas that collect water are not as easy to detect. Those include flower pots, cracks in sidewalks, recycle bins, dips in the driveway and partially clogged gutters.

Witman says if you have an area of poor drainage where eliminating standing water is difficult, BTI tablets can be placed in the water to eliminate mosquito larvae. She says BTI is safe for home use and has a low toxicity profile for humans and animals.  She says it’s actually made from a soil bacterium.

Witman adds that the web site, www.westnile.state.pa.us, is a good resource for information on the virus, from the latest statistics for tips on reducing mosquito bite risk.

For point of comparison, Texas has already had 381 confirmed human cases of West Nile Virus this year and Mississippi and Louisiana have reported at least 60 cases each.

Horse Euthanized due to West Nile Virus

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A horse in northeastern Pennsylvania had to be euthanized due to West Nile Virus earlier this month.  The horse in Northampton County was diagnosed with the virus by blood test in mid-March, the earliest report of the illness in a horse in Pennsylvania since the disease first appeared in the state.

It’s believed the mild weather has brought mosquitoes out early in some areas.  Amanda Whitman of the Department of Environmental Protection says the virus is difficult to predict, but the unseasonably warm temperatures have led to an increase in the number of mosquitoes much earlier than in years past. DEP does not begin full time monitoring for the season until April.

In 2010 and 2011, the first equine cases were not reported until August.  Whitman says it’s a reminder not to wait to take steps like eliminating standing water around your home to control the population of mosquitoes.

To learn more about West Nile Virus, you can go to DEP’s West Nile web page, where you will find statistics and advice.

Heavy Rains Boost Mosquito Population

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If you’ve been swatting more mosquitoes lately, you can lay some of the blame on Hurricane Irene and Tropical Storm Lee.   The back to back storms left a lot of standing water, where mosquitoes are likely to breed.

 Kevin Sunday, spokesman for the state Department of Environmental Protection, says they started noticing more mosquitoes showing up in some of the traps in the north central and south central parts of the state. In one trap, which usually caught 25 mosquitoes, was capturing in the hundreds, and in some occasions in the thousands of mosquitoes.  

Sunday says they were seeing about 25% more of the mosquitoes that carry the West Nile Virus before the storms, since the flooding there’s been another increase of about 10%.

DEP has been doing extra control operations across the state to bring the mosquito population down. That effort will continue for another month. PEMA and the state Department of Health had asked DEP to collaborate and do additional sprayings.

Sunday says people can help by eliminating as much of the standing water around their properties as possible. He says wheelbarrows, jammed gutters and even overturned Frisbees can collect enough water for mosquitoes to breed.

Sunday adds that people should also take steps to keep mosquitoes out of their homes, checking to make sure screens are intact. He says wear long sleeves and use insect repellant when you have to work outdoors in the evening when mosquitoes are out.

First Probable Human West Nile Virus Case in Pennsylvania This Year

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Pennsylvania has its first probable human case of West Nile Virus this year.   An elderly Lebanon County woman was hospitalized in late July with a high fever and neurological symptoms.  Officials say she is currently recovering from what they believe is West Nile Virus.

So far this year, mosquito samples in 54 counties have been identified with the West Nile Virus.

 Severe human infections from the mosquito-borne virus can cause encephalitis or inflammation of the brain along with high fever, headache, neck stiffness, disorientation, tremors, convulsions, paralysis and coma.  There is a milder form of the infection known as West Nile fever that may produce head and body aches, skin rash and swollen glands.  Unusually, the infection does not result in any illness.

More Mosquito Activity in 2011

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State and local officials have stepped up their West Nile virus surveillance efforts this summer, as mosquito samples have already tested positive in 39 of Pennsylvania’s 67 counties.  That’s up from 37-counties all of last year, and 33 counties in 2009.  “While we are seeing a similar number of positive samples, we are seeing it in a broader geographic area,” says Kevin Sunday with the state Department of Environmental Protection (DEP).  He says it’s most likely due to heavy rains.  “Stagnant water that would collect after any rainfall is fertile breeding ground for mosquitoes.”

Since mosquitoes breed anywhere water can collect and become stagnant, Sunday says there are simple precautions you can take at home.  They include everything from cleaning clogged gutters to turning over any wheelbarrows that can collect water.  “So we encourage everyone to dump out any standing water on their property, to drill holes in the bottom of their recycling containers, if not already.” 

West Nile virus has been in the United States since at least 1999, according to the Centers for Disease Control and Prevention.  It affects the nervous system, and can result inflammation of the brain.  However, there have been no human cases of West Nile virus reported in Pennsylvania this year.    

The DEP reported numerous mosquito samples that tested positive last week.  They include Fayette County’s first positive test since 2005 and Tioga County’s first positive test since 2003.  Sunday says, “We are taking aggressive surveillance action across the state.”

Pennsylvania's West Nile Virus Map - 08/08/11

This DEP map shows where West Nile virus has been detected in 2011.