West Nile virus still a concern as summer ends in New York City

Summer may be coming to a close, but don’t count out New York City’s mosquitoes just yet.

Steamy temperatures help keep the buzzing bloodsuckers active and breeding — extending the season for them to carry and transmit the West Nile virus across the five boroughs.

“The hot weather does have an impact,” said Mario Merlino, assistant commissioner at the city Health Department’s Bureau of Veterinary and Pest Control Services. “We have an extensive network of traps in the city. We are looking for [West Nile virus] positive mosquitoes everywhere.”

West Nile virus is potentially deadly, especially for those over the age of 50 and those with compromised immune systems. At its worst, the virus causes encephalitis and meningitis. But some who contract it may only develop mild symptoms, such as fever, headache and fatigue.

So far this season, eight New Yorkers have tested positive for the virus. Six developed serious symptoms, while two suffered mild or moderate related illnesses. Three other people showed no symptoms but the virus was discovered when they donated their blood.

The virus has been identified in mosquito pools in all five boroughs, with the highest numbers in Queens and Staten Island.

Health officials are urging New Yorkers to stay vigilant by using insect repellent, draining standing water and wearing long sleeves and pants in the evening and early morning hours when mosquitoes are most active.

Mosquito season is widely defined as April through October, with the population dwindling as the nights become colder. But it’s not unusual to see the hearty insects in November.

“Mosquitoes can hang on longer than you think,” said Stephen Morse, a professor of epidemiology at Columbia University’s Mailman School of Public Health. “This isn’t the time to become complacent.”

The mosquito-borne virus first made headlines when it was discovered in Queens in 1999. It has since spread throughout the country with health officials creating a complex annual monitoring system. The city treats breeding areas by periodically spraying pesticides from trucks.

“When we do find positive mosquitoes in a trap, we put supplemental traps around it,” said Merlino. “We don’t want to spray areas that don’t need to be treated.”

Despite a spike in mosquito-borne diseases during the Zika virus outbreak several years ago, most New Yorkers take the annual West Nile threat in stride.

Merlino said the city continues to inform the public about the virus at community events, and pages of information can be found on nyc.gov/health, including a map of positive findings and a pesticide spraying schedule.

Migrating birds may also be an important factor in transmission of the virus, Morse said.

“Culex pipiens (the mosquitoes that carry West Nile virus) really prefer birds,” he said. “When the birds go, the mosquitoes concentrate on us.”