SOUTH KINGSTOWN, R.I. — Labor Day marks the end of the summer season, but thanks to generous amounts of rain and warm temperatures, state officials are warning a seasonal pest is sticking around into the fall and is just as dangerous as ever.

Mosquitos don’t traditionally conjure up images of pestilence; for most residents they’re a minor and sustained annoyance to anyone spending time outside in the summer. Despite their minuscule size, mosquitos in Rhode Island carry and transmit two blood-borne diseases to watch out for: eastern equine encephalitis (EEE) and West Nile virus.

“This year’s clearly a higher-than-normal risk for eastern equine encephalitis,” said Alan Gettman, the mosquito abatement coordinator for the Rhode Island Department of Environmental Management. “Based on evidence for other states in southern New England, it’s more prevalent out there now than it normally is for this time of year.”

Gettman demurred on whether climate change is a reason, but noted that generally more rain means more mosquitos, and Rhode Island has had a wet summer this year. The mosquitoes’ active season is getting longer as well; mosquitos are active primarily in the warm summer months, before slowing down until the first fall frost kills them off for the year.

More mosquitoes are a bigger risk to state residents; more mosquitos overall means residents are more likely to be bitten by an infected mosquito that can transmit West Nile or EEE. While both viruses are relatively rare, with only a few reported cases in the United States each year, they are both serious illnesses.

About 30% of people who develop EEE die, with survivors of the virus developing ongoing neurological problems. West Nile virus, meanwhile, was first reported in Rhode Island in 1999, and causes symptoms in about one in five infected people. About 1 in 150 people die of the virus — a New Hampshire man died from the virus in late August, state officials there reported.

Gettman runs the state mosquito abatement program. During the warmer months, he traps mosquitoes around the state to try and pinpoint where the infected insects are. This year, said Gettman, they found EEE at Chapman Swamp in Westerly, around the Great Swamp Management Area, and around a mile away from the University of Rhode Island campus in South Kingstown.

Earlier this year, DEM announced it found 17 positive EEE and five West Nile in tested mosquitos. Rhode Island isn’t alone. Connecticut officials earlier this year announced they found 27 instances of EEE in mosquitoes and another 192 with West Nile.

“This one mosquito species inhabits exclusively hardwood freshwater swamps,” Gettman said. “This is the species that is known to maintain EEE in the environment year after year, whether we see it or not.“

Gettman said the species is known for drawing blood from different bird species that are known as carriers of EEE. Another 50 species of mosquito inhabit separate aquatic habitats, ranging from stagnant water in backyards, tree holes, or municipal catch basins.

“The more time the mosquito has to bite per bird,” Gettman said, “the [better the] likelihood the virus gets transferred back and forth between the bird and mosquito and mosquito and bird.”

In late August, DEM announced it had hired a contractor that would use a helicopter to drop pellets with a mosquito larvicide known as Bti, a naturally occurring bacteria, to kill mosquito larvae before they become adult mosquitos.

The larvicide was applied over two days across 3,000 acres of Chapman Swamp and the Great Swamp Management Area. Earlier this year the town of Westerly conducted its own aerial spraying around Chapman Swamp for mosquitos.

DEM closed all access points to Great Swamp while the larvicide was being applied.

Bti is the department’s preferred management strategy when it comes to mosquitoes over aerial spraying, which it performed once in 2019. The bacteria is embedded in corn cobs that are dropped into the kind of waters mosquito larvae like to grow in.

“The goal here is to kill the larvae before they emerge and become adults,” said Ken Ayers, DEM’s agricultural division chief. “Bti is very commonly used for mosquito control for several decades, and it kills pretty specifically the larvae that start life in the water or wetlands.”

The lifespan of a mosquito on average tops off at one or two months. Gettman said the oldest mosquitos are always the ones most likely to carry West Nile or EEE. By applying a larvicide in areas where mosquitoes are confirmed to carry the virus, it cuts down the chances of an adult mosquito spreading the viruses into humans into September and October before the first frost.

“The mosquito threat doesn’t end until the first heavy frost,” Ayers said. “And it’s getting later due to climate change. It varies where you are in Rhode Island, but it’s [usually] mid- to late October, and there’s literally over another month to go. Plenty of time for things to happen and plenty of risk out there.”

The larvicide treatment won’t permanently end the presence of mosquito-borne viruses in Rhode Island. Officials from DEM and the Rhode Island Department of Health still recommend taking personal protective steps to reduce mosquito bites, and limiting the overall exposure to mosquitos.