An insect-borne virus may have killed more than 1,000 deer in southwestern Pennsylvania this year, and officials said it appears to have struck earlier and wider than previously.

The Pennsylvania Game Commission said Tuesday that epizootic hemorrhagic disease has been confirmed in a third Pennsylvania county, Beaver, and tests are being performed to see if it has reached Allegheny, Cambria or Westmoreland counties.

The disease had previously been identified throughout Greene County and in several Washington County townships.

Deer decompose quickly, making it difficult to know precisely how many have died from the outbreak, but a fatality figure of more than 1,000 is suggested by reports from the public and observations by staff members, the commission said.

The state wants to hear from people in southwestern Pennsylvania who encounter dead deer. The carcasses need to be tested within 24 hours to produce reliable results.

State wildlife officials said hunters in hard-hit areas will find it more difficult to locate deer, so they might want to scout for alternative hunting grounds for the coming season.

Epizootic hemorrhagic disease cannot be contracted by humans and rarely manifests clinical signs in such traditional livestock as cattle, sheep and goats. Farmed deer and elk, however, are susceptible.

The disease is spread to deer by biting midges and is normally fatal within five or 10 days. Visible symptoms include excessive drooling, weakness and loss of fear of humans. Cold weather usually ends any outbreak by killing the insects that spread the virus.

As a precaution, hunters should wear rubber or latex gloves when they handle or field-dress any animals, and wash their hands and tools afterward.

Epizootic hemorrhagic disease was suspected in the death of a few dozen Adams County deer in 1996, but tests were inconclusive. It was confirmed in a 2002 outbreak that killed 70 deer in Greene and Washington counties and reached Maryland, Ohio, Virginia and Wisconsin.

This year, the disease has struck in Kentucky, Tennessee, Indiana, Virginia, Ohio and West Virginia.