Mosquito in Oak Bluffs tests positive for West Nile Virus

— File photo by John Tann

The Massachusetts Department of Public Health (DPH) notified Island health officials Thursday that a mosquito tested positive for West Nile Virus in Oak Bluffs, the third positive result on Martha’s Vineyard in the past month.

On July 30, a mosquito tested positive for the virus in West Tisbury, and on August 13, another mosquito tested positive in Tisbury.

West Nile Virus is most commonly transmitted to humans from the bite of an infected mosquito. Most people never develop symptoms. A few will experience flu-like symptoms, and a very small percentage will develop serious conditions including encephalitis or meningitis.

DPH still classifies Martha’s Vineyard as a low risk for human infection. Several communities in the Boston area, southeastern Massachusetts, and the mid-Cape have been elevated to moderate risk because of positive tests.

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.