What should vacationers pack in their travel medical kit?

It's a scary world of diseases out there, even for a vacationer.

And that's why it's a good idea to pack a travel medical kit.

What you take depends on where you're going, what you'll be doing and how long you'll be staying. It will include personal medications, like cholesterol-lowering drugs or inhalers for asthma and first-aid basics like bandages, aspirin and antibiotic ointments. You'll definitely need more supplies if you're headed for a place with mosquito-borne diseases like dengue — whether it's a beach in a tropical paradise, a South American jungle or a destination in India or Africa.

For suggestions, we talked to three travel medicine experts about what travelers should bring and also what they should do or avoid doing to stay healthy.

Our advisers are Dr. Lin Chen, director of the Travel Medical Center at Mount Auburn Hospital in Boston; Dr. Davidson Hamer, director of the Travel Clinic at Boston University; and Dr. George Rutherford, head of the Division of Infectious Disease Epidemiology at the University of California, San Francisco. They know from their own — and their patients'-- experiences how critical a kit can be. Here's their suggested supplies — and some useful tips.

1. Mosquito repellent: bring it or buy it there

Let's start with the tourist who wants to kick back and relax at a posh beach resort — say, a Caribbean island or Mexican resort town.

You'll likely eat and sleep in air-conditioned rooms. You might enjoy a screened patio. But eventually, you'll head outside and need a mosquito repellent. The Centers for Disease Control and Prevention recommends mosquito sprays containing DEET, picardin or oil of lemon eucalyptus. A well-stocked hotel gift shop — in tourist magnets like Cancun or Cabo San Lucas — knows what its guests need. "If you're going to be visiting places that cater to tourists, they're going to carry products with DEET," says Chen.

If you're staying outside tourist areas but in a place with plenty of retail outlets, can you count on buying repellent?

Probably — but maybe not. A health scare like the dengue virus can send locals and visitors alike clamoring for repellents. "I talked with a group of students doing research in the Dominican Republic," says Chen. "They brought their own DEET but used it all up. When they went to buy more, the shelves were all empty." Some of the students got mosquito bites and came down with chikungunya, she says. "If it's possible, bring your own products — and enough to last," she says. Products containing 25 percent DEET or higher will protect for 10 to 12 hours, though they might need to be refreshed if people sweat, or swim. 2. Beware of dusk ... and trees

Even if you think you've covered every bare inch of yourself with repellent, a wily mosquito can find that one square inch you missed. Say you're at a resort in in the Solomon Islands in Oceania, a place with a high risk of malaria. The anopheles mosquitoes that carry malaria bite at dusk and dark, and they like to gather under trees to breed and hide out in tree holes. "If you're standing under a tree at dusk, wearing a bikini, with a drink in your hand and think you're not going to get bitten by a mosquito, you're delusional," says Rutherford. Cover your arms and legs with clothing or repellent, he says. Better yet, don't stand under trees at dusk! 3. Use sunscreen the right way

In tropical spots, the sun is a potential hazard. Pack or purchase sunscreen that protects from both UVA and UVB rays and is rated at least SPF 15. And if you're in need of both sunscreen and mosquito repellent, the CDC recommends putting sunscreen on first because it is designed to be absorbed into the skin. After it dries, use the repellent, designed to stay on top of the skin.

4. Check the risk of malaria

What if you're really roughing it, in the bush of Africa or the jungles of Latin America or rural villages in Asia?

Repellents alone aren't enough. "A key thing is whether an area has malaria," says Hamer. "If the risk is moderate to high, an anti-malarial is essential." The CDC has a list of areas in the world where malaria is a risk to travelers. You need to start the prescription before you go, take it during your trip and continue for a prescribed time after returning home. 5. BYOBN: Bring Your Own Bed Net If there's a risk of malaria, and you don't know what your accommodations will be, bring an insecticide-treated bed net. "Use it in rustic settings or in a private home that may not have good screens," says Chen. The CDC says the nets, which come in a variety of sizes, should reach the ground. Depending on the ceiling height from which a net hangs, if it doesn't reach the ground, tuck the bottom ends under the mattress so mosquitoes can't get in. Look for a net that has long-lasting insecticide treatment, developed to repel mosquitoes for up to three years. The World Health Organization has given full or interim approval to 15 such bed nets. They're available in a variety of sizes, from small to extra large, and generally cost less than $30. 6. Long sleeves, long pants

If you're hiking in Costa Rica, or the forests of Peru, sand flies can get you, and they carry leishmaniasis, a disease that causes sores or damage to internal organs.

DEET is only moderately effective against sand flies, Chen says, so cover exposed skin with long sleeves and long pants. Since sand flies generally bite between twilight and dawn, try to stay inside when the sun is down. Sand flies are found in Central and South America as well as parts of Asia, the Middle East and North Africa. 7. Turn a scarf into a shield

Here's a tip if you find yourself outdoors with a lot of bugs around. Before you go, spray a fairly large scarf with permethrin, a repellent for use on clothing, shoes, bed nets. "It's safe to use, even on fine fabrics like silk," says Chen. "If you get to a particularly buggy place, take it out and wrap it around any exposed area of your body." The treated scarf should remain protective through four to six washings.

8. Don't forget condoms

We hate to pry, but are you a going on a sex adventure?

"That's why [travel medicine experts] have to ask what they'll be doing on their trip," says Rutherford. A Bangkok sex tourist would benefit from a hepatitis B vaccine about a month before traveling, and condoms should be in the medical travel kit. And because Zika has been found to spread sexually from an infected male to his partner, "sexual exposures in Zika lands is a bad idea," he says.

9. Bottled water is best, unless...

Drink bottled water — that's the resounding chorus of advice. But check out that bottle. "I stayed at a hotel in India, and the bottled water looked kind of dirty," says Hamer. "I asked where it came from, and they said, 'We fill it from the tap.' I've probably traveled to more than 80 countries, and there's almost no place where I haven't been able to find bottled water. But make sure the seal is intact."

10. Be a food fanatic

Eat peeled fruit, and beware of fresh salads, beautiful garnishes or salsas because they might have been washed in contaminated water. Eat foods that are steaming hot, and "take a towel and bottled water, and rinse off utensils before using them," says Hamer. That way, you'll know that their last rinse and wipe has been with uncontaminated water.

11. If diarrhea strikes...

If curiosity or good manners made you eat or drink something your stomach regrets, be prepared. "Make sure you have Pepto-Bismol or Imodium for an upset stomach," says Chen. "We don't recommend using it lightly, but for severe traveler's diarrhea, you might bring a prescription antibiotic." With all the fears about overusing antibiotics, Hamer suggests taking them as last resort. Drinking a lot of water, along with Imodium, should be all it takes if the problem is limited to one or two loose stools a day, he says. "But if you're having many loose bowel movements a day, with a fever or blood in the stool, take an antibiotic."

12. Pill power

Will you be traveling on the water? You might pack some seasickness pills, says Hamer. Or climbing mountains? Ask your physician to recommend a drug to combat altitude sickness.

Bring an antihistamine, even if you don't think you have allergies. "Sometimes people run into something they didn't know they were allergic to," says Chen.

13. Consider a mask

Air pollution is severe in places like India and China. "If you have lung disease, bring an inhaler, even if you haven't had to use it for years," says Chen. "Pollution can trigger a flare. It's not a bad idea to wear a mask. And if you want to exercise, do it indoors."

14. Do your research

Each country presents its own health challenges.

The Centers for Disease Control and Prevention has country-specific recommendations for immunizations as well as other medical advice for travelers. "When travelers call [the Travel Medical Center at Mt. Auburn in Boston], we tell them that's a very good resource to start with," says Chen. The International Society of Travel Medicine has a global clinic directory to help you find specialized practitioners who will make individual recommendations before you go, during your trip via phone or email, and after you come home. 15. Buckle your seatbelt Inadequate roads, old jalopies and risk-taking cab drivers can be as dangerous as disease-carrying mosquitoes. "Buckle your seat belt," Rutherford says. "And if your cab doesn't have seat belts, get out." Copyright 2019 NPR. To see more, visit https://www.npr.org.