As cases rise around the world, U.S. health officials are warning Americans about dengue fever, a potentially deadly disease transmitted by mosquitoes. The disease is endemic – or ubiquitous – in many parts of the world, including Puerto Rico and other U.S. territories. And each year, cases are reported among Americans returning from travel, as well as through local transmission in some states, including Florida, Hawaii and Texas.
But this year is different. Massachusetts, where the disease has historically been rare, has reported 50 traveler infections so far in 2024 and is on track to hit a record number of annual cases. Puerto Rico has declared a state of emergency, the U.S. has reported more travel-related cases than would normally be expected (745, according to the Centers for Disease Control and Prevention), and local transmission is also occurring. In Florida, for example, seven cases have been reported, including two in the Florida Keys.
The CDC warns of an increased risk of dengue fever for Americans, but says the risk is still generally low. Still, we asked experts what you can do to protect yourself. Here’s their answer.
What to do: On an individual level at home
First, it’s important to know that the risk of being bitten by a dengue-infected mosquito near your home is low if you live in the continental U.S., according to the CDC. But there are steps you can take, experts say.
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Protect your body. The most important steps you can take to protect yourself are “applying mosquito repellent, avoiding areas known to have a lot of mosquitoes, and wearing clothing that doesn’t expose a lot of skin,” Dr. Amesh Adalja, an infectious disease expert at Johns Hopkins University, tells Yahoo Life.
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Make your home less inviting to mosquitoes. You can protect your home from mosquitoes by “removing trash from your yard,” says Adalja. Mosquitoes breed in standing water and thrive in the areas around them, so removing or covering things like sandboxes, plastic pools, or other trash and containers where water might collect can help slow population growth and discourage mosquitoes from making themselves at home in your home.
What to do: Travelling on an individual level
To put this into perspective, since the beginning of 2024, 2,391 cases of dengue fever have been reported in U.S. states and territories, according to the CDC. The vast majority of these (1,498) have been reported in Puerto Rico, where the virus is endemic. Another 794 people have been infected while traveling, while only 99 cases have occurred locally outside Puerto Rico.
The data is clear: The greatest risk is when traveling, especially to countries with high rates of dengue fever. According to the CDC, that includes most countries and territories in Central and South America, including Mexico, Puerto Rico, Costa Rica and Brazil, several countries in Africa, and parts of Southeast Asia. A full list can be found here. When traveling, you can protect yourself by:
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Stay away from areas where mosquitoes live. Adalja recommends asking your hotel, tour guides or other locals where there are a lot of mosquitoes and avoiding those areas if possible.
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Gear up. Just like at home, try to cover your skin as much as possible and use mosquito repellent, advises Adalja.
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Take care of your legs. The species of mosquito that transmits dengue fever, Aedes aegypti, “is very shy and skillfully hovers around people to find the perfect opportunity to land and bite quickly,” Chad Huff, spokesman for the Florida Keys Mosquito Control District, tells Yahoo Life. “Often they concentrate on the lower legs and ankles, where they are less likely to attract attention or slaps.” So you should take extra care to cover and protect your lower body.
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Watch for symptoms. Although up to 80% of dengue cases are asymptomatic, you should be aware of how you feel if you’ve been bitten by mosquitoes while traveling to a place with high dengue activity. Symptoms include high fever, headache, body aches, and nausea (“which probably makes people think they have COVID,” says Adalja). If you have these symptoms, see a doctor and tell them about your recent travel and bites so they can test you. While most illnesses are mild, the infection can cause potentially fatal internal bleeding, so you may be prescribed antiviral treatment. Adalja says antiviral treatment may also be advisable if you live in areas within the U.S. that currently have high dengue activity, including Key West, Florida.
Although the rising number of dengue cases worldwide is a cause for concern, Adalja says people don’t need to cancel their travel plans. “It’s a globally endemic disease,” he notes. The CDC recommendation “doesn’t say against travel, it just says it’s riskier.”
What to do: At the public health level
The species of mosquito that transmits the dengue virus, as well as yellow fever, chikungunya and Zika, is still prevalent across the country. “I think there’s a lot of laxity” in terms of “vector control,” or efforts to keep populations of potentially disease-carrying mosquitoes low, Adalja says. To better combat dengue outbreaks, local, state and federal officials can:
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Monitor mosquito splashes. It’s not just people who can (and should) be tested for dengue and other mosquito-borne diseases. County health departments can collect the insects from the slimy pools they’re drawn to and test them for a range of viruses. Some places do this (Austin, Texas, recently discovered two pools that had West Nile virus), but a 2022 survey found that only about 24% of surveillance programs are “fully functioning.”
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Conduct public clean-up activities. It’s one thing for everyone to do their part to keep their own yard clean, but public trash provides even more opportunities for mosquitoes to breed, says Adalja. Communities — whether local or state — “can organize cleanups of areas with a lot of mosquito breeding grounds, similar to what happened in Miami Beach when there was local transmission of the Zika virus there,” says Adalja.
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Use mosquitoes against yourself. “The most effective approach is when (health officials) release genetically modified sterile male mosquitoes, as they have done in Key West, Fresno, California and parts of Texas,” says Adalja. Tests of this approach in other countries have shown it can reduce dengue cases by as much as 97%. Adalja says there is a stigma around genetic modification in the U.S., but adds that releasing mosquitoes infected with bacteria or irradiated can also help control populations.
