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Penn State Extension West Nile Virus Program Administrator Thomas Smith demonstrates the trap used to collect mosquitos for research as he suggests ways to prevent an increase in the mosquito population in York, Pa. on Wednesday, Sept. 2, 2015.

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York County leads the state in the number of mosquitoes that have tested positive for West Nile Virus.

Seventy-one additional samples collected during the last two weeks of July tested positive for the virus, according to Penn State Extension York County's West Nile Virus Program.

West Nile is an illness originating in Africa that can cause a rare and sometimes fatal condition in humans.

Officials say the total 241 positive samples found in York County make it the leader in the state. Philadelphia and Delaware counties hold the second and third spots, respectively.

More: York County mosquito population high this summer

Thomas Smith, administrator for the York County West Nile program, was not surprised to see the spike.

"The water and the warm temperatures kind of go hand in hand with what the mosquitoes need," he said.

Standing water left from the flooding definitely increased concerns, though in many areas, waters have receded compared to Dauphin and Cumberland counties, he added.

Human case suspected: Pennsylvania officials are sounding the alarm about mosquitoes as testing is underway to confirm the suspected first case of human West Nile virus infection in the state this year.

The state is checking the case of an Allegheny County resident, sending samples to the Centers for Disease Control and Prevention.

West Nile has infected more than 150 people in the state over the past six years.

The Department of Environmental Protection says it has found mosquitoes infected with the virus in 51 of Pennsylvania’s 67 counties.

Limiting skin exposure and the use of insect repellants can help combat the spread of the virus.

Stopping the rise: Smith has said that cleanup is important to prevent mosquito populations from rising.

Urban or suburban areas where there are a lot of people not picking up after themselves and not maintaining their swimming pools exacerbate the problem. All pools should be covered when not in use, and owners should check that those covers are not holding water, Smith said.

Some municipalities have contacted the program because of the high number of positives they're seeing, and many residents are calling, emailing and reporting other concerns through the program or the state website, he said.

Because of all the rain, the county has seen an increase not just in West Nile carriers, but other flood-related and nuisance mosquitoes, according to Smith.

For example, the Asian tiger species — a daytime biting mosquito — lays eggs in empty containers before they collect water. Some lay eggs in low-lying wooded areas and remain dormant for decades until water is introduced, he said.

The county is "being hit with everything at one time," Smith said.

Program staff continue to spray for mosquitoes in municipalities that are deemed high-risk areas, but that only accounts for the insects that are flying at the time. It's done primarily to reduce human disease risk from West Nile-bearing species, Smith said.

More: York County a breeding ground for West Nile virus

Smith warns that the spraying will not do much to reduce the population if people do not clean up at the same time — the population restores otherwise.

Program staff, along with the Department of Environmental Protection, are doing additional surveillance and sampling as a result of the high number of positives. Much of their efforts also  have been geared toward larval surveillance, he said.

Staff will treat stagnant water with pesticide that kills mosquitoes before they become adults because they're easier to target, Smith said.

York County has 31 different kinds of mosquitoes  of the more than 60 across the state, Smith said,

The breakdown: Program staff and DEP Vector Management collected positive samples from 14 municipalities and York City, from July 19 to 31.  

The highest number of positives were from Springettsbury, Manchester, Lower Windsor and Conewago townships — which had between five and 26. Others had three or fewer.

They are listed below, in order of highest to lowest:

  • Springettsbury Township - 26
  • Manchester Township - 13
  • Lower Windsor Township -8
  • Conewago Township - 5
  • Spring Garden Township - 3
  • Windsor Township - 3
  • Hellam Township - 2
  • Penn Township - 2
  • York City -2
  • West Manheim Township -2
  • York Township - 1
  • West Manchester Township - 1
  • Hanover -1
  • East Manchester Township -1
  • Dover -1

— The Associated Press contributed to this report.

 

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