Despite the vast amount of scientific information we have on how to prevent illnesses when traveling, much misinformation persists. Here are six things you may have heard relating to the risks of getting sick when abroad, especially when visiting developing nations—but should not accept as fact. At best, there is just a nugget of truth behind some of these notions and pieces of advice.
1. Drinking alcohol with meals helps prevent traveler’s diarrhea.
Don’t count on it. Several lab studies have found that wine can reduce levels of bacteria that can cause foodborne illnesses (including Salmonella, Shigella, E. coli, and Bacillus cereus), possibly related to the organic acids in wine in synergy with the alcohol. And some observational studies, including one in Epidemiology in 2002 and one in Eurosurveillance in 2003, found that people who consumed red wine (equivalent to about three 5-ounce glasses) or beer (three 12-ounce bottles) were less likely to get sick during Salmonella outbreaks. But none of these small observational or lab studies prove that drinking alcohol is a good strategy for avoiding traveler’s diarrhea (you won’t find it recommended on the CDC website). Moreover, based on the research, it may take quite a bit of alcohol to have any possible benefit—more than what the Dietary Guidelines for Americans and other health authorities advise (up to one drink a day for women and two for men).
2. Taking a probiotic supplement prevents traveler's diarrhea.
Don't count on that, either. A meta-analysis of 12 studies, published in Travel Medicine and Infectious Disease in 2007, concluded that taking different kinds of probiotic bacteria (Saccharomyces boulardii and a mixture of Lactobacillus acidophilus and Bifidobacterium bifidum) may prevent traveler’s diarrhea. But other studies have produced conflicting results, including no benefit at all, and so far there aren’t enough well-designed trials with positive results to recommend the use of these supplements. Probiotic supplements also vary greatly in formulations, and there is no regimen detailing what should be taken, how often, and in what dosage. Moreover, the label claims on the products often don’t match what’s actually in the bottle: That is, buyer beware. For more reliable ways to prevent and treat traveler's diarrhea, see Traveler's Diarrhea: Causes and Treatments.
3. If you were born in a foreign country, moved away, and then returned to visit, you don’t have to worry about getting sick there.
That’s not true—you are as vulnerable as any non-native tourist. People build up natural immunity to many of the microbes in their environment, such as to those in drinking water and those transmitted by mosquitoes. But that immunity fades when you move away. The CDC notes that people who have emigrated to the U.S. from countries where malaria is endemic, such as India, are at particularly high risk for acquiring the disease when traveling back to their homeland or visiting other malaria-ridden places. Among the reasons: They often consider themselves immune since they were born or grew up in a malaria-ridden country, and so may be less likely than other travelers to take proper precautions when visiting, such as taking anti-malaria drugs and avoiding mosquito bites.
4. If you take prophylactic medication for malaria, this will also protect you from other mosquito-borne diseases.
Not true. Though malaria, dengue fever, Zika, and chikungunya are all infections spread by mosquitoes, different organisms are involved. Thus, prophylactic medication used to prevent malaria will not be effective against any of these other diseases, for which there are no medications or vaccines available at this time in the U.S. The only way to avoid these other mosquito-transmitted infections is to avoid mosquito bites. Interestingly, unlike the mosquitoes that carry malaria, which are active at night or at dawn and dusk, the mosquitoes that spread dengue, Zika, and chikungunya are active during the day, as well as at night, particularly in well-lit areas.
5. Mosquito-transmitted diseases are mainly a risk in jungles—not urban areas.
Not true. For example, though how it is transmitted varies, the virus that causes yellow fever can be present in both urban and jungle environments (in the jungle, mosquitoes spread the disease to humans after biting monkeys, while in urban areas, mosquitoes spread it after biting infected people). As another example, the mosquito-transmitted Japanese encephalitis virus, which causes a serious infection of the brain, can occur in rural environments with watery rice paddies (where mosquitoes multiply) and even around urban areas, where people may be in contact with pigs or wild birds that are hosts for the mosquitoes. Then there's malaria, which is prevalent, to a greater or lesser extent, in all types of areas—jungle, rural, and urban. In countries where malaria is endemic, the only places where you are not at risk are where there are no mosquitoes, such as at very high altitudes and in the desert (excluding desert oases), or during the cold-weather season in some areas.
6. A street dog has to bite you in order to give you rabies.
Not so. Many people think the only way to get rabies is to be bitten by an infected street dog, and it's true that rabies is usually transmitted by such a bite (through the dog’s saliva). But it’s possible, though rare, to be infected through licks and scratches from the animal. And it’s not just dogs that can spread rabies, but also other infected animals, such as raccoons, foxes, and bats. In fact, if you awaken to find a bat in your room, short of having the bat tested for rabies (an unlikely scenario), you should seek medical attention to discuss if you should get the rabies vaccine, since a bat bite can be hard to see and is easily overlooked.