While the virus is here on the island, the risk of transmission to humans is low according to doctors. NewsdayTV's Shari Einhorn reports.  Credit: Newsday/Staff


West Nile virus first appeared in New York more than 20 years ago and has been detected here annually ever since. The infectious disease can lead to serious illness and death for some people while only mild symptoms in others. Mosquitoes infected with the virus have been found in Nassau and Suffolk counties this summer. Here is what you need to know about West Nile virus:

What is West Nile virus and where does it come from?

West Nile virus is the “leading cause of mosquito-borne disease” in the continental United States, according to the Centers for Disease Control and Prevention. Humans usually contract it through the bite of an infected mosquito. It was first discovered in Uganda in 1937 and spread to other countries. The first U.S. outbreak took place in 1999 in New York, with the epicenter in Queens.

Some people who are infected experience no symptoms at all while others suffer headaches, body aches, joint pains, vomiting and diarrhea. The most severe illnesses associated with West Nile virus affect the central nervous system and include encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes that surround the brain and spinal cord), according to the CDC.

Data from that agency shows that between 1999 and 2022, there were 1,126 cases of West Nile virus reported in New York, including 253 in Nassau and 142 in Suffolk.

How does this West Nile virus season look so far this year on Long Island?

A: Surveillance in both counties has detected infected mosquitoes in several locations, including Lindenhurst, Riverhead, West Babylon and Woodbury. There are no human cases to date in 2023.

“West Nile virus is endemic to the area and we find mosquitoes containing West Nile virus every year,” said entomologist Scott Campbell, chief of the Arthropod-Borne Disease Laboratory at the Suffolk County Department of Health Services. “The amount does fluctuate year to year.”

He said the current season is about average so far.

“We still have a couple of weeks left to really see the true trajectory of the season.”

Campbell said that a wet spring season followed by a hot, dry summer can lead to years with higher amounts of virus because those conditions boost mosquito breeding.

“You could have a hurricane come through and, and basically reset the clock,” he said. “With the violent storms that we had, we actually saw a decrease in the number of mosquitoes because of mortality. A lot hinges on weather and just how the next couple of weeks will play out.”

Who is most at-risk of contracting West Nile virus?

"Since West Nile virus is transmitted by mosquitoes, anyone infected by an infected mosquito is at risk," said Dr. Andrew Handel, a pediatric infectious diseases expert at Stony Brook Children's Hospital. "But encephalitis is by far more common in older adults and immunocompromised people. West Nile virus encephalitis in children is very uncommon."

People who are more than 60-years-old are at greater risk for severe illness if they are infected, according to the CDC, as well as those with medical conditions such as cancer and kidney disease.

Handel said about one-quarter of infected people will experience non-specific symptoms like fever, headache, and a diffuse, red, blotchy rash. Encephalitis is very rare, he said, occurring in about 1 in every 200 people infected.

What can people do to protect themselves against West Nile virus?

Most human cases of West Nile virus are reported in August and September, aligning with the mosquito season.

“Make sure there is no standing water because you don’t want to contribute to the problem of having mosquitoes breeding in your area,” Campbell said.

Handel said people should protect themselves when they are outside by using insect repellent, noting those with 20-30% DEET are recommended. He also said wear long sleeves and pants, and avoid areas dense with mosquitoes when they are most active — around sunrise and sunset.

"You don't want to be bitten by mosquitoes, even though the infection rates are very low," said Campbell. "We see cases of West Nile almost every year."

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