The West Nile virus has not yet been detected this year in Schuylkill County but that doesn't mean it won't be.
Matt Helwig, the West Nile virus coordinator from the state Department of Environmental Protection, said it's hard to predict how far-reaching the virus will be this year.
"It's really a temperature-driven phenomenon," he said Thursday.
The virus is most often spread by mosquitoes but also through blood transfusions, organ transplants, breast feeding and during pregnancy, the Centers for Disease Control and Prevention said in a fact sheet.
The virus causes flu-like symptoms and can result in encephalitis, an inflammation of the brain. Those infected can show symptoms in three to 14 days after being bitten by a mosquito.
No cases of West Nile were found in the United States before 1999 and it was first detected in Pennsylvania in 2000. It is named after the area in Uganda where it first appeared in 1937, according to www.westnile.state.pa.us.
This year, the first reported cases in Pennsylvania were found in Harborcreek Township, Erie County, and in Straban Township, Adams County. The mosquito samples were collected May 22 and May 23 respectively, according to DEP.
Last year, the virus was detected in mosquitoes in 10 municipalities in Schuylkill County: the boroughs of Minersville, Ringtown, Cressona, Schuylkill Haven and West Mahanoy and the townships of North Manheim, Pine Grove, West Brunswick and Mahanoy. The first case of the virus in the county last year was June 19, when a mosquito sample tested positive in Mahanony Township. No human cases of the virus were detected in Schuylkill County last year.
Statewide in 2012, 3,656 cases of the virus were confirmed, according to DEP. Sixty human cases were reported in the state and four people died.
The first case of the virus in the state for 2012 was detected in a mosquito May 3 in Exeter Township, Berks County. It was the earliest case since testing started in 2000, the state Department of Health said previously.
Helwig attributed the warm spring to the rise of the virus early last year.
"The first detection from year to year often varies," he said.
Helwig said he collected mosquitoes in Schuylkill County last month. Samples are collected from areas that are likely to have the most mosquitoes, and if enough of a species is present for testing, it is then sent to a lab in Harrisburg for analysis.
The county has a "remote risk" of having the virus, according to the westnile.state.pa.us. The rating is determined by how many mosquitoes are found to carry the virus in a given county, Helwig said.
The two counties where the virus was found so far this year, Erie and Adams, are classified as having a low risk.
Amanda Witman, DEP spokeswoman, said in an email that, "spraying probably won't start in full force until sometime in mid-June, when we begin to see higher populations."
Helwig said removing standing water from yards is the single most important thing residents can to do reduce the spread of the virus.
"There's 64 different species of mosquitoes in Pennsylvania," he said. "They breed in containers. They are an urban type of mosquito."
Nationwide, 286 people died because of the virus in 2012 - the highest since the disease was detected in 1999 - and it was found in 48 states, the District of Columbia and Puerto Rico, according to the CDC. The total number of people infected in 2012 was 5,674.
Those 50 and older are at higher risk for getting seriously ill from the virus. About 1 in 150 will develop a serious illness but about 80 percent of people will show no symptoms at all they are sick, the CDC said.
Those symptoms could include a fever, body aches and other side effects. Serious side effects can include death, coma and tremors.
Kait Gillis, spokeswoman for the state Department of Health, said Friday that "we've had a cooler spring" than last year but residents should not drop their guard when combating the virus. They should try to avoid being outside during dusk and dawn, when mosquitoes are most active, wear clothing that covers the entire body, and use insect repellent that contains DEET.