7 Symptoms of Dengue to Watch For, According to Experts

Dengue is a viral infection that’s on the rise, with many countries reporting a record number of cases this year.

“Dengue is the most prevalent mosquito-transmitted pathogen in the world, with 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.”

However, that doesn’t mean we’re not at risk for dengue right here in the United States. “The biggest risk factor for U.S. residents is that we travel to other countries,” says Herrera. This year, Puerto Rico has declared a public health emergency, while a higher-than-expected number of dengue cases have been identified among U.S. travelers, especially in those returning from Brazil, Costa Rica, Cuba, Guatemala, Honduras and Mexico.

There have also been reports of localized transmission in places such as Florida and Texas. Localized transmission means people who have not traveled outside the U.S. have been bitten by a local mosquito that’s 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 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 symptoms, 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.

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.

Photo of Aedes mosquito.

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.”

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

The most common symptom of dengue is fever (which can range from mild to 104 degrees) and other symptoms, including:

• Muscle aches and pains
• Pain behind the eyes
• Bone pain (leading to its common name of break-bone fever)
• Nausea and vomiting
• Swollen glands
• Rash, anywhere on the body

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 abroad and at home:

• Get country-specific travel information from the CDC before you travel to help you plan and pack, says Gray. Check here for current travel notices from CDC.
• 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 pre-term birth, low birth weight or neurological abnormalities, says Herrera.
• Pack 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.
• Consider wearing permethrin-treated clothing and hats, which are pre-treated with insect repellant, says Gray.
• Use EPA-approved insect repellants, which have been proven safe and effective. “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, picaridin, IR3535, oil of lemon eucalyptus and 2-undecanone.
• 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.
• Ensure you protect every exposed skin surface. “They’re very good at finding areas you didn’t treat,” says Gray. Don’t forget your face, back of the neck, ears and hairline, and reapply according to label instructions.
• If you’re also using sunscreen, apply it first, let it dry, then apply insect repellant.
• Make sure your lodging has air conditioning and/or screens on the windows. Or pack a bed net, 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.
• Pay attention to public health department alerts about locally-acquired cases so you’re aware of local risk, says Gray.
• Be diligent about eliminating 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, pet water bowls, tarps, and even flower pot saucers. For areas you can’t drain, toss in mosquito dunks containing a naturally occurring bacteria 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.

While there’s no need for alarm, you should be aware that dengue is a risk to travelers, and that you should take steps to prevent getting bitten. Most importantly, “if you have traveled recently to a dengue region and have a fever and other symptoms, inform your doctor,” says Herrera. Your healthcare provider can request a blood test for dengue, although test sensitivity decreases after the first seven days of infection.

Also, be aware that severe dengue symptoms may occur as the fever goes away. Warning signs include symptoms such as abdominal pain or tenderness, vomiting more than 3 times in 24 hours, lethargy and restlessness. Severe dengue is a medical emergency that requires hospitalization.