Travelers' Diseases

Some examples of important diseases that may be acquired through eating contaminated food or drinking contaminated water include:

• Travelers' diarrhea can be caused by a variety of bacteria, viruses, and parasites found throughout the world. These microbes can be found in water and food wherever sanitation and food handling practices are poor or inconsistent. Some diarrhea caused by viruses or bacteria may develop within a few hours of infection and may go away on their own without treatment. Other illnesses caused by certain bacteria, such as salmonella and shigella, have a 48-72 hour incubation period (the time from exposure to the development of signs and symptoms). Diarrhea caused by parasites, such as giardia, tends to have a longer incubation time and, without treatment, may become chronic illnesses in some individuals.
• Hepatitis A virus (HAV) can cause liver inflammation and jaundice,. A vaccine that protects against hepatitis A is available. It is given in 2 doses. The first shot provides protection after 4 weeks. The second shot, given about 6 months after the first, provides lasting protection.
• Cholera is extremely rare in the U.S., but can be found in other parts of the world, such as Haiti and the Dominican Republic, as well as in areas of Africa (e.g., Burundi, Cameroon) and Asia (e.g., Afghanistan, India). People who travel to areas where cholera is a risk very rarely become infected because they typically have better access to safe food and water and do not visit areas where outbreaks are occurring. A vaccine is available and is recommended for travelers who will be going to areas where cholera is active.
• Typhoid fever is an illness caused by the bacterium Salmonella typhi that can be life-threatening. It can cause prolonged high fever, stomach pains, weakness, loss of appetite and headache. Though rare in the U.S., it is still common in developing nations, especially south Asia. Most cases (up to 75%) that occur in the U.S. are in people who have recently traveled internationally. A vaccine is available for those traveling to areas at risk.

• Malaria is an infectious disease caused by Plasmodium parasites that are primarily spread by the bite of infected female Anopheles mosquitos. Cases of malaria in the United States are rare; they mostly occur among those who have travelled to parts of the world where malaria infections are common (endemic). Most infections occur in Africa, but malaria also exists in regions in Central and South America, parts of the Caribbean, Asia (including South Asia, Southeast Asia, and the Middle East), Eastern Europe and the South Pacific. Preventive medications are available for malaria. They need to be taken daily during your travels and for a specified time after you return.
• Other travelers’ infections associated with bites from insects include viruses such as, dengue fever, chikungunya, West Nile virus and yellow fever. A vaccine is available for yellow fever, and proof of vaccination may be required for entry into some countries. Dengue fever is becoming more common and causing progressively larger epidemics. Zika virus has gained attention recently because it can cause severe birth defects and other health problems in babies whose mothers become infected during pregnancy. Pregnant women should avoid travel to areas where there is a risk of Zika. If they must travel to such areas, they should take precautions against mosquito bites.

Some illnesses spread through coughing and sneezing (respiratory secretions) are less common in the U.S. but may be encountered while traveling abroad. Examples include:

• Tuberculosis (TB)—TB is an infectious disease caused by Mycobacterium tuberculosis that primarily affects the lungs (pulmonary TB). TB is spread when a person with active, infectious TB disease coughs, sneezes, or spits, releasing droplets containing TB bacteria into the air, which are then inhaled by someone else. Although the number of cases have decreased dramatically in the U.S., international travelers are at increased risk for TB.
• Measles, mumps, rubella—these viral infections are less common in the U.S. due to vaccination programs. They are more common in other parts of the world and you may become infected if you have not been vaccinated or if you have but your immunity has waned.
• Influenza (flu)— The CDC recommends that everyone 6 months old and older get a flu shot each season. In particular, people who are at high risk of complications from the flu should receive the vaccine. These include young children, the elderly, residents of nursing homes and other long-term care facilities, pregnant women, and people with pre-existing conditions such as asthma, COPD, heart disease, and liver or kidney disorders.

Sometimes it is important to identify the cause of disease in travelers, not only to treat the individual but also to prevent transmission and to document the prevalence of the specific disease, both in returning travelers and in the countries they visited.

Tests performed will depend on signs and symptoms and the disease suspected. People who return from travel with an acute or chronic condition should consult with their healthcare provider, who may suggest a consultation with an infectious disease and/or tropical medicine specialist.

Below are some examples of tests for infections associated with digestive tract signs and symptoms. Including traveler’s diarrhea.

• Molecular tests may be used to detect the genetic material (DNA, RNA) of microbes infecting the digestive tract. These types of tests are gaining in use, but may not be available everywhere. A GI pathogens panel simultaneously tests for the presence of multiple disease-causing (pathogenic) microbes in a stool sample. The panel of tests detects the genetic material (RNA or DNA) of some of the more common pathogens. It can identify co-infections (more than one microbe causing infection) and identify microbes that might be missed with traditional testing.
• Though used less commonly now, a stool culture may be used to identify causes of bacterial diarrhea.
• Parasitic causes of diarrhea can be identified through the O&P (ova and parasite) stool test. This test is used to identify parasites and their eggs in a fresh or specially preserved stool sample. For some parasites, such as Giardia intestinalis (lamblia), Entamoeba histolytica, and Cryptosporidia antigen tests, which identify proteins associated with the parasite, have been developed.
• Because identifying the cause of viral diarrhea is complex, viral causes of diarrhea may not be tested unless the virus causes a large number of people to become ill, such as an outbreak of norovirus on a cruise ship.

The following are some examples of tests for infections associated with bites from insects, such as mosquitoes.

• The parasite that causes malaria (Plasmodium species) infects red blood cells. It can be identified by collecting a blood sample and examining specially stained "thick and thin" blood smears on slides under the microscope. A rapid antigen assay also has been developed to detect the malaria parasite from a blood sample without a microscopic examination.
• Depending on an individual’s travel history, one or more viruses may be tested such as
  • West Nile virus
  • Dengue fever
  • Zika virus
  • Other arboviruses

Depending on travel history, vaccination history and signs and symptoms, tests for infections spread through respiratory secretions may be done. Examples include:

• Tests for tuberculosis (TB)—a TB screening test may be done to determine whether you have been exposed. If an active infection is suspected, then AFB testing may be done
• Several infections are prevented through vaccination but testing may be done if it is suspected you are not immune and have signs and symptoms. Examples include:
  • Measles and mumps testing
  • Rubella
  • Influenza testing

Sometimes X-rays or CT scans may be used to evaluate specific organs, such as the lungs or liver, for evidence of infection or damage.

Advance planning can help prevent many travelers' diseases. Prior to a trip, you should consult with a healthcare provider to discuss your travel plans, verify that you have been vaccinated as needed, and determine whether you require any booster vaccines to maintain your level of protection. Since many vaccines take time to become effective or may require more than one dose, it is advised that you consult with a healthcare provider 4 to 6 weeks before you leave on your trip. Many medical centers affiliated with academic universities have a travelers' clinic where those preparing to go abroad can obtain expert advice. The CDC website has a page that will help you Find A Clinic. 

Vaccines that may be needed include:

• Hepatitis A
• Hepatitis B
• Influenza (flu)
• Japanese encephalitis
• Measles, mumps, and rubella
• Meningococcal meningitis
• Pneumococcal
• Polio
• Rabies
• Tetanus and diphtheria
• Typhoid fever
• Varicella (chickenpox)
• Yellow fever
• Cholera

Read more at the Centers for Disease Control and Prevention (CDC) Travelers' Health interactive web page.

When it comes to diseases spread by mosquitoes, ticks, flies, and other biting insects, your first line of defense is to protect yourself against insect bites. To avoid insect bites:

• Wear long-sleeved shirts and long, loose-fitting pants. Both should be light in color. Tuck pant legs into socks.
• Use EPA-registered insect repellents containing DEET, picaridin, oil of lemon eucalyptus (OLE), or IR3535m. Use these products only as directed, and pay close attention to their instructions for use by pregnant women and children.
• Treat shoes, socks, pants, bedding, and tents with the repellant permethrin.
• Sleep in rooms that are screened against insects, or sleep under a mosquito net.
• Avoid or empty water from sites where mosquitoes breed, such as buckets, pots, or old tires.
• Carefully inspect your hair, skin, and clothing for ticks after outdoor activities.

If you are traveling to areas where malaria is prevalent, your healthcare provider may recommend preventive medications, such as mefloquine or chloroquine, to begin taking prior to departure. These medications need to be taken regularly during travel and for a specified time period after you return home.

There are several steps you can take to prevent food- and water-borne illnesses during travel. Precautions to take in developing countries include:

• Avoid tap water. This includes refusing ice in drinks, because the water used to make the ice might be contaminated. Allow drinking glasses to air dry before putting beverages into them. Do not brush your teeth with tap water. Do not swallow water while showering or bathing.
• Drink beverages made with water that has been boiled for a minimum of 1 minute, but preferably 3 minutes.
• Drink water that you treat yourself with iodine or chlorine tablets used according to directions.
• Drink canned and bottled beverages. Be sure the caps on bottled beverages are still sealed before you drink them. Wipe the rims of cans and bottles before drinking/pouring if they are wet when you receive them.
• Don’t swim in potentially contaminated fresh water, such as ponds or rivers. Even swimming pools with inadequate chlorination pose a risk. Talk to your healthcare practitioner if your trip will include water-based activities.
• Avoid raw fruits and vegetables. Eat only food that has been cooked and is still hot or fruit that you know has been washed in safe/treated water and you have peeled yourself.
• Other foods to avoid include:
  • Raw or undercooked meat, poultry, seafood, and eggs
  • Unpasteurized milk and milk products, especially soft cheeses
  • Prepared food that has been left unrefrigerated for several hours, especially food containing meat, poultry, eggs, and dairy products
  • Food prepared by street vendors