A mosquito trap in northeast San Antonio has tested positive for the West Nile virus, the leading cause of mosquito-borne disease, according to the Metropolitan Health District.

The data was collected from one of Metro Health’s 30 seasonal mosquito surveillance sites; thus far it is the only trap to test positive.

“Just because one trap tested positive, it doesn’t mean that [the virus] is more around in that area and that it is not in other areas,” said Anita Kurian, assistant director of Metro Health’s Communicable Disease Division.

“The idea here is to increase awareness that mosquito season is here and the mosquitoes that we have in our community do carry West Nile virus,” she said.

Kurian advised all San Antonians to take preventative measures to make sure they don’t get bitten by mosquitoes.

“There is no effective vaccine [for West Nile virus], and there’s no treatment, so the best prevention is to avoid mosquito bites,” she said.

Metro Health recommends those outside dawn to dusk wear long sleeves and pants, and use mosquito repellant with DEET on the outside of clothing as well as exposed skin, as mosquitos can bite through thin fabric.

Every year during its summer surveillance, Metro Health’s vector control team usually identifies one to two West Nile Virus-positive mosquito pools in the area, said Kurian.

The samples that tested positive were collected from a mosquito trap around the O’Connor and Nacogdoches Road area on August 4, according to Metro Health, and sent for testing on August 8.

Metro Health was notified of the positive lab results for the West Nile Virus late Tuesday evening and alerted the public Wednesday.

The vector control team treated the nearby area by spraying bacillus thuringiensis israelensis and using mosquito dunks to ensure residents are protected within a mile and a half radius of the testing location.

However, this week’s rainfall may result in increased hatching of mosquito eggs, the department warned.

Metro Health encouraged residents to remove standing water on their property after rains, including in vases, pet water bowls, flower pot saucers, discarded tires and trash cans. Where possible, cover open containers.

Water contaminated with organic matter, like animal waste, or plant material can increase the chances that mosquito larvae will survive, as it provides food for larvae to eat.

Most people who are infected with West Nile virus do not feel sick, said Kurian. Nearly a quarter of people who become infected will develop a mild illness, including fever, headache, tiredness and muscle aches. About one in 150 individuals will develop serious, even fatal, illness. Older people and those with certain underlying conditions are at greater risk of severe illness.

If someone tests positive for West Nile virus, the patient’s health provider is required to report the infection to Metro Health. So far this year, there have been no positive cases reported, said Kurian.

The West Nile virus is common in the U.S., Kurian said, but hasn’t been seen much in San Antonio lately. In 2021, one mosquito pool tested positive, said Kurian, while the last time someone tested positive for the virus occurred in 2020.

Metro Health will continue mosquito-trapping until the end of the fall and will monitor for human cases of the virus.

Raquel Torres is the San Antonio Report's breaking news reporter. A 2020 graduate of Stephen F. Austin State University, her work has been recognized by the Texas Managing Editors. She previously worked...