What are they?
“Travelers' diseases” is a broad term for bacterial, viral, fungal, and parasitic infections that may be acquired when someone travels away from home, especially when traveling from a developed or industrialized area to a less developed area. (Some of the conditions discussed in this article, however, can be acquired while at home, not just while traveling, such as HIV and hepatitis). Every travel destination and every geographical location has its hazards, including home. Those who live in a place, however, are generally aware of their own diseases and dangers and do their best to make accommodations for them. In Montana, for instance, you don’t feed the bears, you avoid poison ivy, stay aware in rattlesnake habitat, wear long-sleeved clothes during tick season (to avoid Rocky Mountain Spotted Fever), don’t drink the water from mountain streams (to avoid the parasite Giardia lamblia), avoid black widow spiders, treat all rodent droppings with care (to avoid hantavirus), and wear insecticide to avoid bites from mosquitoes carrying West Nile virus.
While bears and spiders and snakes are outside the scope of an article on microorganisms, it illustrates the need for visitors to a region to evaluate the risks that they may encounter. Staying in an urban hotel in a developed country for a few days can be very different from a two-week outdoor adventure in tropical South America. Travelers should educate themselves and discuss with their doctors their destinations, expected lengths of stay, and planned activities. With the proper care, many traveler’s diseases are preventable – through avoidance of the carrier’s (vector’s) environment, avoidance of risky behaviors, vigilant care with food and water, chemoprophylaxis (medicines taken before and during travel to prevent a specific illness), and vaccines.
Traveler’s diseases can be acquired through contaminated food or water, from animal droppings, and from soil. Close exposure to infected animals and physical contact with animal hides can also put someone at risk. People will usually not be able to see, smell, or taste the contamination. Diseases are also carried by vectors such as biting mosquitoes, flies, and ticks. Some can be acquired from swimming in freshwater and by walking on the beach with bare feet, while others are passed from person to person – through close contact, needle sharing, blood, and unprotected sex. The symptoms of some diseases may be so mild and self-limited that they go unnoticed; many may be a miserable annoyance for a few days, and a few may cause an acute medical emergency. There are diseases that may not emerge until the traveler has returned home, with symptoms that may resolve, cycle, grow progressively worse, or linger. Left untreated, a few of the diseases can lead to blindness, organ failure, coma, and death.
The most frequently encountered traveler’s illnesses are diarrhea, nausea, vomiting, fever, and skin manifestations (rashes, sores, swelling, etc). Also seen are hepatitis (liver inflammation) and its accompanying jaundice, headaches, meningitis and/or encephalitis. Some diseases will also cause respiratory symptoms – coughing and/or difficulty breathing.
Some diseases are global in nature - they are found throughout the world and, unless prevented through vaccination, frequently cause childhood illnesses. In some cases, these illnesses can lead to lifelong complications. Many nations have vaccination programs to decrease the number of people who contract conditions such as measles, rubella (German measles), mumps, and polio. In areas that are unable to uniformly vaccinate their populations, these conditions can be endemic and/or there may be epidemics of the disease. Travelers who are not protected through previous vaccinations, young children who have not been fully immunized, and patients who are immunocompromised may be at an increased risk of contracting one of these infections. Adopted children from foreign countries and immigrants to the United States may bring these and other traveler’s diseases with them to the U.S. and should be evaluated for them.
Travelers' diarrhea can be caused by a variety of bacteria, viruses, and parasites throughout the world. These microorganisms are found in water and food wherever sanitation and food handling practices are poor or inconsistent. People are often acclimatized to their own local bacteria and viruses but affected by microorganisms in other places. Parasites can affect both local inhabitants and those who travel.
Some viral and bacterial diarrheas tend to occur within a few hours of infection and may be self-limiting. Some, such as Salmonella and Shigella, have a 48-72 hour incubation period. Parasitic diarrheas tend to have a longer incubation time and, without treatment, may become chronic illnesses in some individuals.
Hepatitis A virus (HAV), which can cause liver inflammation and jaundice, can also be acquired from contaminated food and water. Infection with hepatitis B virus (HBV) and/or hepatitis C virus (HCV) may cause symptoms similar to hepatitis A, but they are transmitted through exposure to blood and body fluids, sexual contact, or perinatally (mother to infant). Risky behaviors, such as unprotected sex, may also expose travelers to HIV and other sexually transmitted diseases.
The most common infections associated with fever are malaria, dengue fever, and yellow fever. All of these conditions are carried by mosquitoes, and they are endemic in tropical areas of the world. A vaccine is available for yellow fever, and proof of vaccination may be required for entry into some countries. Chemoprophylaxis is available for malaria. Dengue fever is a rapidly expanding disease (found in more and more geographical areas) that is causing progressively larger epidemics. There is no preventative treatment for dengue; it can be avoided by taking measures to avoid mosquito bites.
Travelers can also catch colds and the flu while in airplanes and other modes of transport while in route to or from their travel destination.
It is important to identify the cause of the 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.
Causes of bacterial diarrhea may be identified with a stool culture and may be treated with antimicrobial agents when symptoms appear and/or may resolve without further tests to identify the pathogen. 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), antigen tests have been developed. These tests identify proteins associated with the parasite and can be useful when parasites are present in low numbers. Because identifying the cause of viral diarrhea is complex, viral causes of diarrhea may not be identified by specific cultures or tests unless the virus causes a large number of people to become ill, such as an outbreak of norovirus on a cruise ship.
The parasite that causes malaria (Plasmodium spp.) 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. Many of the other travelers’ diseases can be identified either by culturing the microorganism, observing it under the microscope, and/or testing for antibodies or antigens. Patients who return from travel with an acute or chronic condition should consult with their doctor, who may suggest a consultation with an infectious disease and/or tropical medicine specialist.
Sometimes x-rays or CT scans may be used to evaluate body 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, people should consult with their doctor and verify that they have been vaccinated for diseases such as mumps, measles, rubella, polio, and tetanus and if any boosters are needed to maintain a protective level of antibodies. They should discuss their travel plans and get additional vaccinations as recommended for diseases such as hepatitis A and yellow fever. If they are going to go to areas where malaria is prevalent, they will usually be given chemoprophylaxis, such as mefloquine or chloroquine, to begin taking prior to their trip. These medications will need to be taken regularly during the trip and for a specified time period after the traveler's return. Some doctors may give their patients antimicrobial agents to take with them along with instructions on how and when they should be taken if symptoms appear during their trip.
Both the U.S. Centers for Disease Control and Prevention and the World Health Organization have current information on traveler health and preventative strategies. They also have up-to-date country and region-specific travelers' disease information (see Related Pages).
In spite of taking every precaution, travelers may still become ill, either during their trip or several months after they have returned home. In general, the earlier that travelers' diseases are detected and diagnosed, the easier they are to treat. Travelers should know which symptoms signal the need to seek prompt medical care in the country they are visiting and which may be safely self-medicated. For several months after their return home, they should note any symptoms that occur and bring them to their doctor's attention.
On This Site
Tests: AFB Culture, CBC, Flu tests, Hepatitis A, Hepatitis B, Hepatitis C, HIV Antibody, O&P, Stool Culture, West Nile Virus, Measles and Mumps
Conditions: Diarrhea, Viral Hepatitis, HIV, Tuberculosis, West Nile Virus
In the News: Neglected Infections of Poverty are 'Hidden Burden' in the U.S. (2009)
Elsewhere On The Web
Centers for Disease Control and Prevention: Traveler’s Health
World Health Organization: International travel and health publication
U.S. Department of State: International Travel
Foreign & Commonwealth Office: Travel Advice by Country
CDC NCID, Division of Parasitic Diseases: DPDx Laboratory Identification of Parasites of Public Health Concern
CDC: Division of Bacterial and Mycotic Diseases
MedlinePlus: Traveler's Health
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
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