There's a Dengue Outbreak In the U.S. Here's What You Need to Know to Protect Yourself

Dengue may sound like a disease that’s only found in faraway tropical locations. But it’s on the rise in many places—and Florida is seeing a record number of cases this year, with nearly 500 cases reported to the CDC to date. Sadly, there also has been one death.

The biggest issue is that dengue virus activity has been found in the local mosquito population. Localized transmission means people who have not traveled outside the U.S. have been bitten by a mosquito that’s carrying the virus. “The local mosquito population has picked up and is carrying the virus. This occurs when a mosquito bites an infected person and then bites someone else,” says entomologist Elmer Gray, University of Georgia public health extension specialist. “This makes humans the reservoir for the virus, unlike other mosquito-borne illnesses, such as West Nile, when birds are the reservoir.”

Dengue is the most prevalent mosquito-transmitted pathogen in the world, with up to 400 million infections globally each year, says Bobby Brooke Herrera, Ph.D., assistant professor, Rutgers Global Health Institute, and assistant professor, department of medicine at Rutgers Robert Wood Johnson Medical School. “It’s most localized to the tropics and subtropics around the equatorial belt,” he adds.

However, that doesn’t mean we’re not at risk for dengue right here in the United States. Typically, the biggest risk factor for U.S. residents is that we travel to other countries, says Herrera. However, with higher-than-normal local transmission and people traveling to Florida for vacations or snowbirding later this fall, it’s important to be aware of the risks of this particular outbreak.

Aedes aegypti mosquito, which transmits dengue

Dengue is caused by four different but related viruses (DENV-1, -2, -3, and -4), or serotypes, which co-circulate and can infect a person at the same or different times. Symptoms begin within about a week of being bitten by an infected mosquito, says Herrera.

Most people with dengue will not have symptoms or only have mild ones, and usually will feel better in about a week. But for others, dengue can progress to life-threatening conditions, including dengue shock syndrome or dengue hemorrhagic fever, says Herrera. The most common symptoms include muscle aches, pain behind the eyes, nausea and vomiting, swollen glands, a rash anywhere on the body, and bone pain (leading to its common name of break-bone fever).

Certain groups, including infants, pregnant women, older people, and those with certain medical conditions, are at greater risk of progressing to severe dengue. Also, some people previously exposed to one serotype may develop worse disease if exposed to another serotype later, says Herrera.

There is no specific medicine to treat dengue, nor is there a dengue vaccine available in the U.S., says Herrera. Treatment includes rest, drinking plenty of fluids to stay hydrated and taking acetaminophen (not aspirin or ibuprofen) to control fever and relieve pain.

Dengue is transmitted by the bite of the Aedes mosquito, with Aedes aegypti the most common vector, or means of transmission. “Aedes aegypti, or the yellow fever mosquito, is a highly effective vector because it feeds primarily on humans and commonly rests indoors,” says Gray. “It has a tendency to take supplementary blood meals and often moves from one residence to another as it deposits a few eggs here and there in small numbers in hidden places.”

This particular mosquito will bite multiple people at one site; so, for example, if you wave it away from you, it moves on to the next person. “This increases the potential to vector the disease because it will feed on multiple people,” says Gray.

Aedes albopictus, the Asian tiger mosquito, is another common vector. Though it’s not the primary vector, there have been outbreaks in other areas with these mosquitoes, says Gray. Other Aedes species transmit the virus in areas such as the Pacific.

Prevention is your best defense against dengue. “This is not just about a mosquito bothering you. It’s about getting very sick,” says Gray. Here’s what to do to protect yourself and family, whether you’re at home in your own backyard or traveling:

• Use EPA-approved insect repellents, which have been proven safe and effective. This is the most important thing you can do to protect yourself when enjoying outdoor activities. “Other products that are not EPA-approved, such as garlic oil, are proven safe but they have not been proven effective,” says Gray. EPA-approved repellants include DEET, IR3535, picaridin, oil of lemon eucalyptus, and 2-undecanone. Don’t forget your face, back of the neck, ears and hairline, and reapply according to label instructions.
• Choose the right product for your activities. “The lower concentration of active ingredient, the more often you will need to apply it,” says Gray. For example, you may be able to use a product with a lower percentage of active ingredients for a few hours of outdoor dining versus an all-day hike.
• If you’re also using sunscreen, apply it first, let it dry, then apply insect repellent.
• Consider wearing permethrin-treated clothing and hats, which are pre-treated with insect repellant, says Gray.
• Wear loose-fitting, light-colored clothing, including long sleeves and pants. “A mosquito has a long proboscis and can bite through tight-fitting fabrics,” says Gray. “Also, choose light colors, which provide less contrast in the environment, so mosquitoes are less able to detect you.” You’ll also transmit less of a heat signature in light clothes.
• Pay attention to public health department alerts about locally acquired cases so you’re aware of risks even when you’re not traveling out of the country, says Gray.
• Eliminate standing water around your home. “No good ever comes from standing water. The species that carry this virus are container breeders, so any standing water can be a place for them to lay eggs and reproduce,” says Gray. That includes kiddie pools, clogged gutters, old tires, pet water bowls, tarps, and even flower pot saucers.
• Watch out for lesser-known hiding spots. Even certain plants that hold water, such as bromeliads or lucky bamboo, can cause problems. “They offer a breeding site for mosquitoes such as Aedes aegypti, which can utilize those small water sources,” says Johnalyn Gordon, Ph.D., assistant professor, urban entomology, at the University of Florida/IFAS Fort Lauderdale Research and Education Center.
• Use mosquito dunks in areas you can’t drain. Mosquito dunks contain a naturally occurring bacterium called Bacillus thuringiensis israeliensis (Bti). This kills mosquito larvae and is specific to mosquitoes and other biting pests, but won’t harm bees, fish, frogs, people or pets, says Gray.
• Make sure your home’s window and door screens are in good repair. Don’t make it easy for mosquitoes to sneak indoors, says Gray.
• Get country-specific travel information from the CDC before you travel overseas to help you plan and pack, says Gray. On top of that, reconsider traveling to regions with dengue if you are pregnant. There’s evidence of transmission from a pregnant mother to her baby, with risk of preterm birth, low birth weight or neurological abnormalities, says Herrera.
• When you return from a trip to a dengue region, avoid getting bitten for three weeks, even if you don’t feel ill; this is in case you are carrying the virus so you do not inadvertently spread dengue to others through a mosquito’s bite, says Gray.

While there’s no need for alarm, be aware that there is a risk of local transmission when you travel and that you should take steps to prevent getting bitten. Most importantly, if you have traveled recently to a dengue region—including Florida—and have a fever and other symptoms, inform your doctor, says Herrera. Your health care provider can request a blood test for dengue, although test sensitivity decreases after the first seven days of infection. Severe dengue is a medical emergency that requires hospitalization.