Only three birds had tested positive on Aug. 14. The number had risen to 30 on Sept. 13.
Bucher said the department has collected seven infected birds from Boonsboro, 13 from Hagerstown, two from Williamsport, two from Clear Spring, three from Smithsburg, two from Fairplay, two from Sharpsburg and one each from Keedysville and Maugansville.
County residents who find dead birds can call a statewide number, 1-866-866-CROW (2769) from 8 a.m. to 8 p.m. Monday through Friday and from 10 a.m. to 4 p.m. Saturday and Sunday.
Preliminary test results received Thursday indicate Toosie, an 8-year-old thoroughbred mare, is the third horse to test positive for the virus in the county, Bucher said. Last week, it was announced that two horses had the virus.
Two of the three horses that have tested positive for the virus are being cared for at Boonsboro's Homeward Bound Horse Rescue stables, rescue group owner Robin Rippeon said Friday.
Test results are not yet in on a fourth horse, Domino, a 10-year-old Arabian, she said. Domino was taken to the stables Sept. 14 to receive 24-hour care after showing symptoms of the virus.
The Frederick County resident who may have the virus was taken to Washington County Hospital by ambulance, but Christoffel said he did not know whether the person was still hospitalized.
Christoffel said the Washington County woman, who is over 50 years old, was not in the hospital. He would not release the woman's hometown for privacy reasons.
Seven Washington County residents have been tested for the virus, but until this week all tests came back negative, Christoffel said.
Area residents need not be alarmed, but they should continue to take steps to avoid being bitten by mosquitoes that carry the disease, he said. Those steps include avoiding the outdoors at dusk when mosquitoes are most active, and using insect repellent.
Some who contract the virus experience flu-like symptoms, such as fever, headache and muscle aches, Bucher said. In rare cases, the virus can result in high fever, disorientation and death.
People older than 50 and those with weak immune systems are most susceptible to medical problems related to the virus, Bucher said.
There is no vaccine against West Nile Virus for humans.
Because mosquitoes can breed in stagnant water found in tires, Christoffel and Bucher urged county residents to get rid of old tires they have during a Washington County-sponsored Tire Amnesty Day on Sept. 28 from 8 a.m. to 2 p.m.
Up to six tires per Washington County household can be dropped off for free at seven sites: Forty-West Landfill, North Hagerstown High School, South Hagerstown High School, Williamsport High School and the Highway Department shops at Keedysville, Greensburg and Indian Springs.