Dengue Fever Is a Health Threat at the Paris Olympics and Here in the U.S. Here’s What to Know and How to Stay Safe

Specifically, the Centers for Disease Control and Prevention (CDC) has issued a warning about the increased risk of dengue fever—a virus transmitted by certain mosquitoes. Although it's usually found in tropical areas, dengue is on the rise in the U.S., with most cases reported so far in Florida, New York, and Massachusetts. (Many are travel-associated, meaning people picked up the virus outside the U.S., but Florida has reported local transmission, which means infected mosquitos are living there.)

Dengue is a concern in Europe, too, and with more than 15 million people expected to visit Paris for the Games, some experts are worried about a more rapid spread. (Thankfully, dengue doesn't spread from person to person, but an infected person could be bitten by a mosquito, which then becomes infected and can spread the virus by biting other people.)

And dengue isn't the only concern this year. Other diseases spread by mosquitos and ticks (think: Lyme, Zika) have been on the rise for the past two decades, per the CDC.

Here, an infectious disease expert explains the spike in these infections and how to keep yourself safe, with tips on how to prevent insect bites naturally.

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Why are dengue and other insect-borne infections on the rise?

It’s no coincidence that as temperatures only seem to be getting hotter, mosquito- and tick-borne infections are on the rise, too. Climate change is a major factor in the increase, says Michael Von Fricken, PhD, MPH, an expert in environmental and global health at the University of Florida and UF Health.

“With less harsh winters, you're going to have a potentially longer tick activity season, and there's going to be more opportunities for them to bite a host,” he explains. That means ticks are emerging earlier than before, giving them plenty of time to find people to bite and infect.

The same is true for mosquitoes, too. Warmer temperatures allow them to lay more eggs and populate faster.

“If it's warmer, they're going to become an adult faster and have more generations of mosquitoes, which can lead to more bites,” Von Fricken says. And more bites unfortunately means more insect-borne diseases.

How to prevent insect bites naturally

Whether you're attending the Olympics or a neighborhood cookout, there's plenty you can do to protect yourself from insect-borne illnesses like dengue and Lyme, and it all comes down to preventing bites in the first place.

1. Wear layers—especially when you're hiking

Because ticks prey in the woods, covering up when you're hiking—even when it's boiling-hot outside—is a must for staying protected. According to Dorothy Leland, the board president for LymeDisease.org, that means building a "protective shield around yourself" with long pants, long sleeves, shoes, socks that your pants can be tucked into so as to hide your ankles, a hat, and a bandana around your neck (pro tip: check out these chic hiking clothes). And don't forget about your hair (yep, ticks can hitch a ride in your locks): Make sure it's in a ponytail or braid, especially if it's long.

2. Spray on some permethrin

Spraying permethrin—an anti-parasite that's used to treat head lice and scabies, per the National Library of Medicine—on your sneakers can do wonders when it comes to fighting off ticks when you're outdoors. "There are studies that show that just protecting your feet can do an amazing job against ticks because they tend to be low to the ground, so their entry point is that they often climb up on your shoes and keep going and get to your skin," Leland says.

3. Use insect repellent

Insect repellent is an obvious solution and is oh-so necessary for fighting off mosquitoes and ticks. But you have to make sure you grab a certain kind: According to the CDC, when it comes to mosquitoes, only repellents that have DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone as an active ingredient will do the trick. But you might as well stick to either DEET, picaridin, or IR3535, as those are the only three that can protect you against ticks, too.

4. Shower and check for ticks

After spending time in the woods, the most important thing you can do is shower and scan your entire body for ticks, including your scalp and your private parts, says David Weber, MD, MPH, a board-certified infectious disease and internal medicine doctor. "Look in your clothes for ticks. Do a full-body check by looking in a mirror, and check hidden spots: behind the knees, the waist area, the belly button. That’s where they like to hide," he says.

And as for your clothes? Toss them in the dryer on high heat, just in case there were any stragglers.

5. Use a fan when you lounge outside

When you simply want to sit outside and enjoy a nice day without worrying about getting eaten alive by mosquitoes, add an electric fan to the mix. According to the American Mosquito Control Association, mosquitoes are relatively weak fliers, so placing a large fan on your deck can provide a low-tech solution. Simply set it on the table next to where you're hanging out, and watch the breeze not only blow them away but also send your scent—you know, the one that tells the pests there's a tasty feast nearby—elsewhere.

6. Practice pre- and post-travel care

The best way to take care of yourself before traveling to a place that might expose you to infection is by being aware (so you can take precautionary steps while you're there). Global health agencies like the European Centre for Disease Prevention and Control are tracking cases of dengue fever to keep an eye on potential spread, which means travelers can see how many cases have been reported in their destination country.

When you get home, disclose the details of your trip to your doctor if you start having any symptoms, Von Fricken says.

For example, if you travel to the Olympics and afterward experience telltale symptoms of dengue, such as a sudden high fever, severe headaches, pain behind the eyes, muscle and joint pain, nausea, vomiting, swollen glands, or a rash, it's important to disclose your travel history to your doctor off the bat. "It's just to make sure that it's not ruled out automatically,” Von Fricken says.

When to see a doctor

Keep in mind that dengue symptoms usually show up between four and 10 days after a bite and last for two to seven days, per the World Health Organization. Luckily, most dengue cases are mild and can be treated at home with rest and pain medication.

It is possible to have severe dengue, though, which in some cases can be fatal. See your doctor right away if you have any of the following symptoms:

• severe abdominal pain
• persistent vomiting
• rapid breathing
• bleeding gums or nose
• restlessness
• blood in your vomit or stool
• extreme thirst
• pale and cold skin
• feeling weak

With tick-borne illnesses like Lyme disease, symptoms often start to appear gradually, per the Mayo Clinic. A common sign of Lyme is a rash that slowly starts to spread and looks like a bull's-eye. Other symptoms include fever, body and joint pain, and muscle weakness.

If you have any symptoms or know that you’ve recently been bitten by a tick, it’s best to see a doctor for early diagnosis and proactive treatment.

—reviewed by Jennifer Gilbert, MD, MPH