The number of cases of West Nile virus found in mosquito samples from Schuylkill County has doubled from last year.

The same is true in Monroe County, and many counties across the state.

Even though the numbers are higher, local county officials said they’re about average — and even less than in some previous years.

“There were 36 West Nile virus samples collected this year, up from 17 last year,” said Kyle Schutt, invasive species program coordinator for the Schuylkill Conservation District.

Overall, the state recorded 3,987 cases of the virus in mosquitoes this year. Last year, it saw 3,035. Each year, the Department of Environmental Protection tests between 1 million and 1.5 million mosquitoes.

No human deaths have been reported in 2025 from the virus in Pennsylvania, however, 61 residents have been infected this year, including one each in Schuylkill and Lehigh counties.

A number of factors can contribute to the number of mosquitoes, including weather and environment. And while it has been dry in recent days, it wasn’t earlier this year, Schutt said.

“The spring and early summer rains that we had created a lot of larval habitat, and elevated adult numbers for most of the beginning of the season, which may have contributed to the higher levels of West Nile virus seen this year,” Schutt noted.

This year’s total is the second highest number of the blood-borne virus that Schuylkill County has had since Schutt began his position.

“The most I have collected was in 2018 when there were 65 positive samples,” Schutt said.

Just like in Schuylkill County, mosquito samples are collected over the spring and summer in Monroe County.

Aaron Lombard, Monroe’s vector control coordinator, said that between 15 and 20 adult mosquito traps are set weekly throughout the county.

Traps are typically placed in populated areas where nursing homes, hospitals, schools and public parks are located, he said. They’re also set near stormwater infrastructure, wastewater facilities, junkyards, recycling centers and construction sites.

“Of the 360 total traps set in Monroe, 56 samples returned testing positive for West Nile virus,” Lombard said.

Last year, it logged 22 cases, but the highest year on record was 2012, which recorded 82 cases.

Lombard said that Monroe — along with neighboring counties of Pike and Wayne — set more traps this year in areas that had been under-sampled in the past.

“The increase in viral activity is largely due to the wider scope of our surveillance and focused targeting of areas prone to breed Culex mosquitoes (those primarily responsible for spreading West Nile virus),” he said.

While more traps were set in mosquito-friendly areas, the number of mosquitoes collected was lower than last year.

“However, these mosquitoes were more likely to be infected with West Nile virus,” Lombard said. “This isn’t to say that there was an increase in West Nile virus this year, but rather we more effectively identified problematic populations and were able to focus control treatments in these areas.”

Lombard said that the controls helped reduce mosquito numbers — but did not completely eradicate them.

“Many of these populations would continue testing positive for West Nile virus in subsequent weeks though the physical number of mosquitoes collected were negligible from a human perspective — not enough to be a nuisance, likely not even enough to transmit the virus to a person, but still detectable via genetic laboratory analysis,” he said.

Lombard said the virus poses a relatively low risk of illness to most healthy individuals.

“In fact, most people who contract the virus never even know they did, and in those that are diagnosed only about 20% show any symptoms, less than 1% have severe symptoms and even fewer than that may pass away,” he said.

According to Lombard, those most likely to exhibit symptoms are typically elderly, immunocompromised individuals or infants.

Still, he said, people should remain mindful of mosquito-borne diseases.

He recommended applying bug repellent, dressing in long sleeves, or wearing netting, as well as avoiding mosquito-heavy areas at dusk and dawn during peak mosquito season.

Lombard added that folks can help stop mosquitoes from breeding.

“This entails not littering, keeping properties clear of items which hold water, reporting natural and artificial mosquito-breeding sites such roadside ditches and stormwater infrastructure, and the proper disposal or storage of tires,” he said.

Schutt agreed, saying the best way to keep mosquitoes away from properties is to eliminate standing water — since that’s where mosquitoes breed.

“This can involve dumping buckets, cleaning bird baths, making sure gutters are not clogged, and avoid having clutter or junk outside,” Schutt said. “Also keeping your yard mowed will help to deter adult mosquitoes from using it as resting habitat and will help keep them away from your property.”

Carbon County had two cases this year, and reported none in 2024. Lehigh County had 207, down from 264 in 2024. Northampton also saw a decrease from 60 to 45 cases this year.

“The numbers can fluctuate significantly year-to-year, weather plays a large part with warmer, wetter years contributing to increased mosquito numbers, however this may not be a direct link to the abundance of the virus, which is largely driven by mosquito interactions with infected birds, which are the reservoir for West Nile virus,” Lombard said.