The World's Worst Travel Diseases

What it is: A potentially fatal disease caused by a parasite, usually transmitted by a bite from an infected mosquito. Chills and headaches are just two of its milder symptoms.

Where it’s found: Large areas of Central and South America, the Dominican Republic and Haiti, parts of Africa, Asia, Eastern Europe, and the South Pacific.

How to avoid it: Ask your doctor to prescribe the appropriate prophylaxis before traveling—usually mefloquine or chloroquine, depending where you’re going. And take measures to prevent mosquito bites, like wearing long sleeves and pants and protecting your skin with a repellent containing DEET.

What it is: An intestinal parasite that causes gastroenteritis, it’s usually contracted by travelers by consuming contaminated water or food. And don’t just blame street food—hikers and backpackers have picked up this awful bug in wilderness areas worldwide.

Where it’s found: Everywhere.

How to avoid it: Stick to bottled or boiled water and be wary of uncooked vegetables. (See the CDC’s recommendations on safe food and water.)

What it is: This virus rears its ugly head in many forms, but hepatitis A is the one most travelers should be concerned with. It can be transmitted through contaminated water or uncooked foods, resulting in either a mild illness or a debilitating, months-long disease that includes fever and nausea.

Where it’s found: High-risk areas include most of the developing world—although outbreaks have been known to occur even in parts of the U.S.

How to avoid it: Hepatitis A vaccine and immune globulin are very effective in prevention, so it’s a good idea to be up-to-date on shots. Otherwise, follow the basic rules of consuming clean food and water. (See the CDC’s recommendations on safe food and water.)

What it is: Most of us know all too well.

Where it’s found: Everywhere—though high-risk areas include parts of Asia, the Middle East, Africa, and Central and South America.

How to avoid it: Watch what you eat and drink—stick to bottled or boiled drinks and avoid raw foods. However, that may not be enough: up to 50% of travelers to high-risk areas will develop a problem over the course of a week or two, according to the CDC. Taking Pepto-Bismol as a preventive measure can also help. (See the CDC’s recommendations on safe food and water.)

What it is: A viral disease transmitted through mosquito bites that can result in everything from an influenza-like syndrome to severe hepatitis and fever.

Where it’s found: Sub-Saharan Africa and tropical South America.

How to avoid it: Yellow fever vaccine is effective and relatively safe. Otherwise, follow the rules of avoiding mosquito bites: wear long pants and long sleeves and use repellents containing DEET.

Note: Some countries require proof of vaccination depending on age and where you’re coming from. See the CDC’s chart.

What it is: A viral disease transmitted by a bite from an infected mosquito that can cause severe flu-like illness.

Where it’s found: South Pacific, Asia, the Caribbean, the Americas, and Africa.

How to avoid it: There’s no vaccine. Follow the rules of avoiding mosquito bites: wearing long pants and long sleeves and using repellents containing DEET.

What it is: A bacterial illness spread by drinking or eating contaminated products. The resulting fever is potentially life-threatening.

Where it’s found: High-risk areas include South Asia and developing countries in Asia, Africa, the Caribbean, and Central and South America.

How to avoid it: There is a vaccine for typhoid, and the CDC recommends it for travelers going to areas where there is a recognized risk of exposure. However, the Centers also warn that it’s not a substitute for careful food and drink selections. (See the CDC’s recommendations on safe food and water.)

What it is: A viral disease transmitted by mosquito bites that can cause debilitating fever, headache, and worse. First isolated in the 1950s, it has been spreading rapidly of late.

Where it’s found: The first instances were discovered on the island of Réunion (near Mauritius). But it has since been showing up in areas of Africa and Asia and even in a limited area of Europe.

How to avoid it: There’s no vaccine, so take precautions to avoid mosquito bites.

What it is: A disease caused by bacteria from infected tick bites that can cause fever, headaches, rashes, and worse.

Where it’s found: This one hits close to home, since infected ticks are found in the northeastern, north central, and Pacific coastal regions of North America. They also inhabit the temperate, forested regions of Europe and Asia.

How to avoid it: If you can’t avoid spots where ticks live, use repellents, which can reduce the risk. Check your skin and hair for ticks each day.

What it is: A virus spread through inadequately treated food or water that can cause acute gastroenteritis. The CDC attributes an estimated 23 million illnesses each year in the U.S. to norovirus.

Where it’s found: Throughout the world. Outbreaks aboard cruise ships have received lots of publicity, but because it’s easily spread, norovirus can appear anywhere where there are lots of people in close quarters.

How to avoid it: Avoidance can be tough, since norovirus is common and easily transmittable. Keep your hands washed and try to avoid “ready-to-eat” cold foods and raw shellfish. (See the CDC’s recommendations on safe food and water.)