West Nile virus found in mosquitoes in West Tisbury

West Nile virus has been found in mosquitoes in West Tisbury. — File photo by John Tann

The Massachusetts Department of Public Health (DPH) announced Thursday that West Nile virus (WNV) has been detected in mosquitoes collected in West Tisbury. So far during the 2013 mosquito season, one mosquito has tested positive in West Tisbury. Last year, there were none.

DPH said WNV is most commonly transmitted to humans by the bite of an infected mosquito.

“The mosquitoes that carry this virus are common throughout the state, and are found in urban as well as more rural areas,” DPH said in a press release West Tisbury health agent John Powers furnished to The Times. “While WNV can infect people of all ages, people over the age of 50 are at higher risk for severe infection.”

Dukes County is currently ranked at the lowest risk level on a DPH map of the state that charts infection risk in four categories from low to critical. Last year, 307 of the 6,828 mosquitoes tested statewide tested positive.

Health officials say the best way to prevent infection is to wear clothing that covers arms, legs, and feet, apply insect repellent while outdoors, reschedule activities from dusk or dawn when mosquitoes are most active, and drain any standing water pools where mosquitoes might breed.

DPH fact sheet

West Nile virus is a mosquito-carried virus that can cause illness ranging from a mild fever to more serious disease like encephalitis or meningitis. It was first identified in the United States in 1999.

WNV is most commonly spread to people through the bite of an infected mosquito.

The majority of people who are infected with WNV (approximately 80 percent) will have no symptoms.

A smaller number of people who become infected will have symptoms such as fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands. They may also develop a skin rash on the chest, stomach and back.

Less than 1 percent of people infected with WNV will develop severe illness, including encephalitis or meningitis. The symptoms of severe illness can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis.

Persons older than 50 years of age have a higher risk of developing severe illness.

There is no specific treatment for WNV infections. People with mild WNV infections usually recover on their own. People with severe WNV infections almost always require hospitalization. Their symptoms may last several weeks and neurological effects may be permanent. Approximately 10 percent of people who develop severe illness will die from the infection.

For more information go to the Department of Public Health.