State health officials say mosquitoes collected in Portland have tested positive for West Nile virus.

They are the first in Maine to come back with any mosquito-borne virus this year, according to the Maine Center for Disease Control and Prevention and the state Department of Health and Human Services.

“Even though it has been dry across much of Maine this summer, the mosquitoes that spread WNV can thrive in this weather,” Maine CDC Director Dr. Puthiery Va said in a release Thursday.

Mosquito pools — groups of up to 50 — are collected and tested routinely in targeted locations across Maine in the summer and fall to detect any viruses before they can spread to humans and domestic animals.

Mosquitoes in Maine also have the potential to spread the eastern equine encephalitis virus and Jamestown Canyon virus, according to the Maine CDC.

“Many infected people have no symptoms. Others experience fever and flu-like illness,” the Maine CDC stated. “Severe symptoms can occur, including encephalitis (brain swelling), and meningitis (inflammation of the spinal cord).

“If you experience any of these symptoms, call a health care provider, especially if a COVID-19 test is negative.”

HOW TO PROTECT YOURSELF

There are steps Mainers can take to safeguard themselves against illness from a mosquito bite, said Bridget Rauscher, Portland’s public health director.

“Despite the dry season, mosquitoes only need a small amount of water to lay eggs, so it’s important to drain any standing water around your property,” Rauscher said in a prepared statement.

Va said that includes birdbaths, pet dishes and empty plant pots.

Health officials recommend taking extra precautions when mosquitoes are most active, at dawn and dusk. They also recommend wearing clothing that covers limbs, using EPA-approved repellent, and using screens on windows and doors.