MA Dengue Fever Cases Come Amid Overall Rise Across Americas

MASSACHUSETTS — Nearly 900 people nationwide, including 17 in Massachusetts, have been sickened with mosquito-borne dengue fever this year amid a larger rise in cases across the Americas, according to Centers for Disease Control and Prevention data.

The relatively rare dengue fever has been more common this year than the more well known mosquito threats: West Nile with three human cases so far this summer, and Eastern equine encephalitis, which has so far only been detected in mosquito samples.

The U.S. cases are among 3 million in the Americas. That's more than at any time in the Americas since 1980, according to a study in the journal Nature that said cases have climbed in the past few years as a result of hotter, more humid conditions that allow mosquitoes to thrive.

In a news briefing earlier this month, World Health Organization officials called dengue fever a "canary in the coalmine of the climate crisis."

This year, 44 states and jurisdictions have reported cases of dengue fever. Florida has the most, with 226 cases. New York has the second-highest case rate, with 74.

Up to 400 million people worldwide are infected every year by a dengue virus, according to the CDC. About 100 million people get sick, and 40,000 die from severe dengue.

Mild symptoms of an infection can be easily confused with other illnesses, according to the CDC. The most common symptoms are a fever; nausea or vomiting; a rash; or aches and pains, including eye pain (typically behind the eyes), muscle, joint or bone pain.

Symptoms typically last from two to seven days, but illnesses can become severe within 24 to 48 hours after a fever has subsided, according to the CDC, which said “severe dengue is a medical emergency” that warrants a trip to a clinic or emergency room.

Symptoms of severe dengue include belly pain and tenderness; vomiting (at least three times in 24 hours), bleeding from the nose or gums; vomiting blood or blood in the stool; and feeling tired, restless or irritable.

People who have had dengue fever in the past are more likely to develop severe dengue. Infants and pregnant women are also at higher risk for developing severe dengue, according to the CDC.

There is no specific treatment for dengue. The best way to prevent dengue is to avoid mosquito bites, according to the CDC. Dengue vaccines are available and recommended for children ages 9-16 who have had a laboratory-confirmed case of dengue, if they live in areas where the virus is endemic. That includes several U.S. territories and freely associated states, but not the United States itself.

U.S. dengue cases have increased from 814 in 2021 to 2,261 in 2022, more than 50 percent of which were acquired in the United States, according to historical data from the CDC. Experts expect the rise to continue with urbanization and climate change.

Another study published in Nature called dengue fever “the greatest human disease burden of any arbovirus.” About half the world’s population lives in an area that is environmentally suitable for dengue transmission.

“In combination with these global trends, rising temperatures attributed to climate change have increased concerns that dengue will intensify in already endemic areas through faster viral amplification, increased vector survival, reproduction and biting rate, ultimately leading to longer transmission seasons and a greater number of human infections, more of which are expected to be severe,” the authors wrote. “Increasing temperatures may further exacerbate this situation by enabling greater spread and transmission in low-risk or currently dengue-free parts of Asia, Europe, North America and Australia.”

Some counties in Florida and Texas are experimenting with genetically modified mosquitoes, a strategy the CDC said has been successfully used in parts of Brazil, the Cayman Islands, Panama and India to control Aedes aegypti mosquitoes, which also spread Zika and chikungunya viruses.

Strategies in other regions with high dengue case rates include eliminating habitat where mosquitoes can lay their eggs, killing the eggs with larvicides and killing adult mosquitoes with insecticides.

Mosquito season in Massachusetts typically ends after the first hard frost, which often happens in October. State health officials have warned residents to take precautions to prevent all mosquito-borne illnesses, including avoiding activity peak mosquito hours at dawn and dusk, wearing repellent with DEET and getting rid of standing water.