What’s bugging state and local government public health officials?

In some Massachusetts towns, public health officials are telling residents to stay inside in an effort to address a big problem caused by a little offender. Mosquitoes are spreading an extremely fatal disease that has public health officials in the Bay State and throughout New England on high alert.

Officials in Oxford, Massachusetts, issued a curfew for outdoor activities late last month in a bid to prevent the spread of mosquito-borne illnesses like West Nile virus, malaria and eastern equine encephalitis, or EEE, the fatal, albeit rare, disease that’s been reported in five states this year so far. 

The EEE virus causes swelling of the brain and kills about 30% of people infected with it. While the U.S. sees on average less than a dozen human cases annually, public health officials in Massachusetts were quick to deem the EEE risk level as critical in four towns after reporting the first human case since 2020 last month. EEE was last a major threat in 2019, when there were 38 cases and 12 deaths along the East Coast and in Michigan.

There is no vaccine for the illness in humans, and its symptoms—which include fever, chills and muscle pain—are often confused with simple flu- or cold-like conditions, so it could go unreported, said Rachel Fay, a researcher in Stanford University’s Department of Biology. It’s a recipe for another public health disaster like the COVID-19 virus outbreak if governments can’t keep up with the increasing risk of mosquito-borne viruses. 

To help prevent the transmission of EEE, schools in Oxford will comply with the voluntary curfew, which recommends people end outdoor activities once dusk hits. While individuals do not have to adhere to the guidelines, they must file paperwork acknowledging they understand the health risks. The town of Plymouth also has a voluntary curfew until Sept. 30, with public parks and fields closing from dusk until dawn.

The advisories come during one of the hottest summers for the U.S., and one of the wettest years as total precipitation from January until August measured more than two inches above average, creating an ideal environment for mosquitoes to thrive. The warnings and curfews also come amid global warnings that mosquitoes are posing a growing threat to public health as temperatures rise.

Summer 2024 was the hottest one on record since 1880, according to NASA. And all signs point to global temperatures continuing to rise in coming years. That’s good news for the bloodsucking insects, which kill 1 million people each year by spreading diseases through their bites, because hotter environments increase how frequently they breed and bite humans, said John Beier, director of the Division of Environment and Public Health in the Department of Public Health Sciences at the University of Miami.

That spells bad news for the U.S., however. Researchers project that as extreme weather such as droughts, heatwaves, floods and rainfall increase in severity and regularity, mosquitoes will spread to new places. Studies have indicated some species will go farther north over the next three decades as temperatures warm, which is “one of the large drivers of increases in vector-borne diseases,” Fay said. The term vector-borne refers to illnesses transmitted to people by ticks, fleas, mosquitoes and other insects.

The U.S., for instance, is already seeing an uptick of West Nile virus, Fay said. Multiple states have reported a seasonal increase in the number of mosquitoes carrying the illness. Rhode Island officials declared a heightened public health emergency last week after five mosquito samples tested positive for the West Nile virus. And more than 200 people across 31 states have contracted the virus, for which there is no vaccine yet, so far this year, according to the Centers for Disease Control and Prevention.

Despite increasing concerns over mosquitoes and their health risks, Beier said state and local agencies’ efforts to manage the insects are effective.

In Plymouth, for instance, in addition to the curfew, the Department of Health is using planes to spray pesticide across the county throughout the night. Communities in California, Florida, Texas and others, are also using aerial sprays to combat potentially deadly mosquitoes.

Mosquito surveillance is another way state and local agencies can manage mosquito-borne illnesses. New York City, for example, released a mosquito surveillance and control plan earlier this year. According to the plan, the city Department of Health and Mental Hygiene uses 53 traps across the five boroughs to capture mosquitoes and test them for viruses they may be carrying on a weekly basis. That data helps public health officials identify the risk of disease to target public health responses, Beier said.

Public education and awareness campaigns are “a promising route” for governments to address increasing mosquito-related risks, said Fay.

Through billboards or social media posts, agencies can communicate the risks of mosquito-borne illnesses and share ways to prevent the spread of viruses. Common suggestions include regularly dumping sources of standing water—where mosquitoes typically lay their eggs—like bird fountains, wearing clothing that fully covers their body or staying indoors during peak mosquito seasons, she said.

But ultimately, Fay said more funding is needed to support research that could improve mosquito control efforts as the changing climate extends mosquito’s transmission seasons and their habitat range.

At the University of Miami, Beier said he is part of a research effort to use sugar-based baits containing an insecticide to trap and kill mosquitoes. The research could add another weapon in public health officials’ response to mosquito-borne illnesses, he said.