A mosquito stands upon human skin. The Louisiana Department of Health says preliminary federal data shows the state has the nation's fourth-highest rate of dangerous West Nile virus infections, so people should protect themselves from mosquitoes. USDA Agricultural Research Service via AP

West Nile virus has been again detected in mosquitoes collected from Zelienople, making it the third time the virus has been found in the borough since late August.

Additional monitoring will be done in the area where these mosquito samples were collected, and appropriate control work will be conducted, said Zoe Heckathorn, of the Mercer County Conservation District, on Friday, Sept. 15.

Businesses and residents located in the borough should take extra precautions such as applying insect repellent and wearing long-sleeve shirts and pants when outdoors during dusk and dawn.

All businesses and residents should reduce mosquito breeding habitat by eliminating standing water, such as bird baths, discarded tires or any other containers capable of retaining standing water, according to the conservation district.

The virus was first detected in the local mosquitoes in late August. The Mercer County Conservation District announced in a Aug. 31 news release that the discovery marked the first time in several years that the virus has been detected in Butler County.

The second sample of mosquitoes in Zelienople detected West Nile again earlier this week, the conservation district said.

According to Heckathorn, West Nile Virus is most common in Western Pennsylvania in August and September, which is when mosquitoes are most active.

Though there a few human cases annually, people are encouraged to deter mosquitoes in areas where the virus has been detected. No human cases of West Nile virus have been reported in Butler County.

Most people do not develop symptoms while some will have fever, head and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash, according to the state Department of Health.

Severe illness can occur in people of any age, but people over 60 years of age are at greater risk. People with certain medical conditions, such as cancer, diabetes, high blood pressure, kidney disease, and people who have received organ transplants, are also at greater risk.

More information about West Nile virus can be found at www.cdc.gov/westnile.