A traveler I’ll call Dad returned home from a trip to Portugal with no appetite and sharp abdominal pains. Weeks later, his eyes turned jaundiced and his nose and taste buds shrank from certain smells and tastes. A doctor diagnosed hepatitis A. During his recovery, Dad attempted to suss out the culprit. The lineup included an oily duck breast and a bowl of steamed clams; he was convinced that the shellfish in Lisbon had done him in.

You don’t have to travel deep into exotica, drink from a fetid pool of water or kiss a chicken to contract a serious illness. Quite the opposite: Viruses, bacteria and parasites debilitate travelers in the most familiar settings. This summer in Yosemite, for example, hundreds of visitors were exposed to hantavirus. Three died. They’d flirted with danger simply by sleeping in a signature tent cabin at Curry Village.

Although we often associate disease with developing countries, Americans heading to, say, Quebec City (Legionnaires’ disease) or Baltimore for a cruise (norovirus) are also vulnerable to infections and diseases.

How do you build up a defense against the microscopic invaders? David Parenti, an infectious-diseases physician and director of the Travelers’ Clinic at George Washington University, recommends some basic strategies. Many will sound familiar to a kindergartner: Wash your hands. Cover your mouth when you cough or sneeze. Don’t put everything in your mouth. He also reminds adults to update their immunizations with Tdap (diphtheria, tetanus and pertussis, or whooping cough) and MMR (measles, mumps and rubella).

I visited Parenti in his office, where he provided an overview of the most common viruses and bacteria and, most important, offered suggestions on how travelers can keep the vacation-crashers away. For additional background information, we consulted the websites of the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO), both invaluable resources for anyone who doesn’t want to bring home that kind of souvenir.


What, where and how: Infected rodents spread this virus through droppings, saliva and urine. Humans catch it by inhaling the diseased particles in enclosed spaces. The virus is common in the American Southwest, especially the Four Corners region (the intersection of Colorado, New Mexico, Arizona and Utah).

An ounce of prevention: Inspect your accommodations for evidence of rodents. If you suspect their presence, change rooms. (Note: Sweeping might eliminate the droppings but not the less conspicuous hazards.) Deter mice by sealing up food and plugging holes or gaps in your lodging.

Do I have it? With the exception of fever, the symptoms mirror the ones you’d experience after a long hike: fatigue and muscle aches, especially in the thighs, hips and back. Parenti also warns of gastrointestinal troubles and respiratory difficulties.

West Nile virus

What, where and how: The mosquito bites a bird, picks up the infection, then spreads the virus by poking its proboscis into a person. The current strain can be traced back to Tunisia and Israel in 1999; since then, it has expanded to Africa, Europe, the Middle East, Canada, west Asia and 48 U.S. states. This year, the CDC documented nearly 70 percent of West Nile virus cases in California, Louisiana, Mississippi, South Dakota, Michigan, Oklahoma, Illinois and Texas, a current hot spot, particularly in Dallas. In the States, the virus thrives midsummer to fall.

An ounce of prevention: Use insect repellent and cover exposed skin with long sleeves and pants. Avoid dawn and dusk, the peak mosquito-feeding hour. Dispose of standing water and check the screens and windows of your lodging for insect-size portals.

Do I have it? Symptoms range from nonexistent (lucky you) to mild (fever, headache, body aches, nausea) to dire (severe headaches, disorientation, paralysis, encephalitis).


What, where and how: This highly communicable virus, aka Norwalk-like virus, is often associated with cruise ships because of the sardine-style living conditions that suit it. Travelers pass it to one another by touching contaminated surfaces or consuming food or water handled by a noro-positive individual.

An ounce of prevention: Wash your hands with the same vengeance as Lady Macbeth. Cruise ships, hotels, resorts and other vacation spots make the ritual easy by placing antibacterial soap dispensers around public spaces. If you notice unsanitary restaurant conditions or food handlers, skip the joint and eat elsewhere. The virus is resistant to high cooking temperatures.

Do I have it? The virus goes right to the belly, meddling with your gastrointestinal tract. Expect a few days of food-poisoning-like symptoms.

Legionnaires’ disease

What, where and how: The Legionella bacteria, named after an American Legion convention in 1976 in Philadelphia where they were first identified, live in natural bodies of water and artificially warm water environments, such as hotel water systems and steam spas. Travelers catch the pneumonialike disease by inhaling the contaminated mist or vapors, such as the spray from a hot tub or shower. In August, three guests at a downtown Chicago Marriott died of the disease (the source: a decorative fountain in the lobby). Also this summer, health officials documented outbreaks in Quebec City, Edinburgh and Stoke-on-Trent, England.

An ounce of prevention: Check the news, including updates by CDC and WHO, for any outbreaks in your vacation destination. In contaminated areas, take such precautions as avoiding jacuzzis and steam rooms. Adds Parenti, “Don’t take a shower.” The alternative: Grab your rubber ducky and hop in the tub.

Do I have it? Legionella causes two types of illnesses: the more mild Pontiac fever (high temperature, headache and muscle aches) and the more serious Legionnaires’ (gastrointestinal discomfort, vertigo, shortness of breath, nasty cough, etc.).


What, where and how: The single-cell parasite inhabits surfaces, food and water sources in areas with compromised sanitation, such as developing countries, campgrounds and parts of Eastern Europe. Travelers can ingest the parasite by swallowing water while swimming, drinking a beverage with contaminated ice and eating uncooked food. Disclosure: On a tour of Budapest, Prague and Poland, I picked up the parasite and we lived unhappily together for a few months.

An ounce of prevention: Drink bottled water or use iodine tablets. If you’re camping, strain the water through a cheese cloth or other sievelike material, then use a traditional filter. Boiling also kills the parasite, but hot tap water won’t do the deed.

Do I have it? You’ll feel as though an angry badger is terrorizing your stomach, causing cramps, bloating and a full complement of gastrointestinal ugliness.


What, where and how: The globe-trotting flu, which includes the strain that caused the swine flu pandemic in 2009, follows a seasonal schedule, typically preying on respiratory tracts in winter (remember to recalibrate the seasons if you’re in the Southern Hemisphere). The virus gets passed around through coughs and sneezes. Because of its easy transmission, tourist attractions are on high alert: The Lincoln Home National Historic Site in Springfield, Ill., for instance, posts informational sheets about the flu in the restrooms at its visitor center.

An ounce of prevention: Pull up that sleeve and get vaccinated in the fall. Also, cover your mouth and nose when sneezing or coughing. If your health is delicate, wear a mask.

Do I have it? Imagine a Tylenol PM commercial: That sniffling, feverish, fatigued, sore-throated and generally miserable person is you.

Avian influenza

What, where and how: This strain of flu exists naturally in wild species but turns life-threatening when it spreads to domesticated poultry and then leaps over to humans. The virus prospers in live poultry markets, such as crowded food bazaars in Asia. Travelers can contract the flu through close contact with infected turkeys, chickens and ducks. Health organizations have also documented cases in parts of Europe, the Near East and Africa.

An ounce of prevention: “Don’t sleep with chickens,” advises Parenti, “and stay away from areas with outbreaks.” The WHO tracks flu incidents: This summer it confirmed cases in Indonesia and Egypt. If you plan to visit a poultry market or farm, scrub your hands, wear a mask and limit your time in these settings.

Do I have it? The symptoms hew to the flu profile: fever, cough, sore throat and muscle aches. More virulent strains can cause eye infections, pneumonia and severe respiratory problems.

Hepatitis A and E

What, where and how: The two strains of viral infections are, for the most part, food-borne. Travelers can become A-positive by drinking (fecal) contaminated water/ice or eating raw produce or shellfish scooped from sewage-soaked water. The CDC warns, “The risk for Hepatitis A exists even for travelers to urban areas, those who stay in luxury hotels, and those who report that they have good hygiene and that they are careful about what they drink and eat.” Hep E is found in untreated water and uncooked pork, deer meat and shellfish. A CDC world map marks hep A as “high” in sub-Saharan Africa, India, Bangladesh, Afghanistan and Pakistan; the agency has documented epidemics of E in Asia, the Middle East, Africa and Central America.

An ounce of prevention: Grit your teeth for the two-dose hep A vaccination. (In the United States, there is no inoculation against E.) Be extremely vigilant with drinking and dining choices.

Do I have it? Both A and E wrack the body with fever, fatigue, loss of appetite, nausea, vomiting, abdominal pain and aches.

Your skin and eyes will also turn yellowish.

Whooping cough

What, where and how: The bacteria invade the respiratory system, causing bouts of violent coughing. Highly contagious, the disease travels by way of sneezing and coughing. Most cases occur in developed countries: This year, for example, 48 states registered a rise in cases.

An ounce of prevention: Adults will require a pertussis booster.

Do I have it? True to its name, the disease causes intense coughing and whooping, with the ragged sound of deep breaths between the hacks.