Officials warn of increased dengue fever, other mosquito disease risk in U.S.

The deadliest animal in the world doesn’t have razor-sharp teeth, claws or tusks.

Because it spreads eastern equine encephalitis, West Nile virus, yellow fever, Zika, chikungunya and lymphatic filariasis, the mosquito holds the grim title of most deadly species on Earth, according to the World Health Organization.

Experts say this season could be a bad one for EEE and other bug-borne diseases.

The CDC issued a warning Tuesday about increased risk of dengue fever across the U.S. The warnings come amid record-breaking global incidence of the mosquito-borne viral disease. One case was reported in Hillsborough County this week, according to the Florida Department of Health. The last time a case was reported in Hillsborough County was 2019, local officials said.

The mosquitoes, also known as Culiseta melanura, are the life’s work of Pioneer Valley Mosquito Control District Director John Briggs. He said there are multiple factors that dictate how things will turn out this year for EEE, or “triple E,” a potentially fatal virus.

“For instance, the virus needs to be present already in the bird population, and weather conditions must remain favorable to Culiseta melanura and other ... mosquito species,” Briggs said.

Once the virus is prevalent in the bird population, it will typically start to spill over into mammal-biting mosquitoes, he said.

Although Briggs said it’s a bit too early for any widespread local transmissions of an arbovirus — any of a group of viruses transmitted by mosquitoes, ticks or other arthropods — viruses like EEE and West Nile are expected to be pervasive this coming season.

Historically, Briggs said human cases in Massachusetts tend to start to pop up around late August through October. In Florida, chances are higher with the summer rains. But, because of the significant rainfall this spring, the National Weather Service predicts a higher likelihood of flooding and an exceptionally active mosquito season.

EEE has serious symptoms that can include fever, headache, vomiting, diarrhea, seizures, behavioral changes and drowsiness, according to the Centers for Disease Control and Prevention. About 30% of infected people die from the disease, and many who survive it must grapple with long-term neurological problems, the CDC notes.

Symptoms of West Nile virus, meanwhile, are absent for about 80% of people infected with the illness. Others, however, might experience high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis, the CDC says.

Monitoring dengue

Briggs said experts are also monitoring the transmission of dengue by mosquitoes. Florida had two local transmissions of dengue so far this year, Briggs said. WHO reports that each year, there are an estimated 100 to 400 million cases of dengue worldwide.

Dengue is a tropical disease that occurs in warm areas where the mosquitoes carrying the disease are found, according to Jeanne Galloway, West Springfield’s director of public health and chair of the commissioners for the Pioneer Valley Mosquito Control District.

When someone contracts dengue, they might experience fever with aches and pains (eye pain, typically behind the eyes, muscle, joint, or bone pain), nausea and vomiting, the CDC says. About 5% of dengue cases can be severe, resulting in shock, internal bleeding and death. Symptoms include belly pain or tenderness, vomiting (at least three times in 24 hours), bleeding from the nose or gums, vomiting blood, or blood in the stool, and feeling extremely tired or restless, the CDC warns.

Like EEE and malaria, dengue represents a significant threat to global public health and is transmitted exclusively through the bite of an infected mosquito.

Like other viruses, the spread of dengue is influenced by travel outside the state and region, where people contract the illness and bring it back to Western Massachusetts. Changes in the climate also can increase incidences of the disease.

“It becomes more palatable for the mosquito species to live in our environment,” Galloway said.

Going into warmer weather, the Mosquito Control District will begin surveilling, capturing and sampling mosquitoes to see what species are in the region, and then later in the month will test the level of disease, Galloway told The Republican.

Prevention

Officials recommend residents avoid getting bit by following these bits of advice: Use Environmental Protection Agency-approved insect repellent; avoid peak mosquito times at dusk and dawn; fix doors and screens to prevent mosquitoes from getting in; and wear long sleeves and pants to minimize the amount of exposed skin available for mosquitoes to bite.

Residents also are urged to deter artificial habitats in their yards by draining buckets, kiddie pools, tire swings, wheelbarrows or any other containers that accumulate water. Galloway said moving water prevents adult mosquitoes from breeding.

“That’s why it’s easier and less annoying if we eliminate or minimize places where they will breed and create adults, so we don’t have to worry about spraying for adults,” she said.

Galloway recommends emptying out the water from potted plants and cleaning gutters to keep water flowing every couple of days.

“Especially during the rainy season, if you’ve got plants and flowers outside in pots where there is water on the top or in the tray underneath, if it has been more than three days, you have the chance of breeding mosquitoes in that stagnant water,” she said.

While Galloway said citronella plants and candles work, they only work within a certain zone, which is not going to be very far from the citronella itself.

Galloway also recommends keeping residential ponds clean with appropriate fish that specifically eat mosquitoes and are natural to the area, or by purchasing biological mosquito-control pellets available for over-the-counter use.

“(The pellets) can only be used in bodies of water on your property. You can put them in your pond if it doesn’t go anywhere, and you can put them in your pool, but if you have a stream that goes by your property, you cannot use them,” she said.

Times staff and the Associated Press contributed to this report.