Travelers' Diseases

Travelers' diseases can be acquired in a variety of ways, depending on the pathogen, such as 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. Some diseases are carried by vectors such as mosquitoes, flies, and ticks. Others can be acquired from swimming in freshwater or 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.

Examples include:

• 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.

For a list of diseases related to travel, including information on their modes of transmission, visit the CDC's web page on Travelers' Health: Diseases.

The symptoms of some travelers' 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 symptoms of travelers' diseases are:

• Diarrhea
• Nausea
• Vomiting
• Fever
• Skin manifestations (e.g., rashes, sores, swelling)

Some diseases will cause:

• Hepatitis (liver inflammation) and its accompanying jaundice and headaches
• Meningitis and/or encephalitis
• Respiratory symptoms (coughing and/or difficulty breathing)

The World Health Organization (WHO) recommends that travelers have a medical exam upon their return if they experience symptoms in the weeks following their travel, or if they have a visited a country where malaria is present and returned with a fever. Those who have chronic diseases, such as cardiovascular disease or diabetes, or who may have been exposed to a serious infectious disease or spent an extended time traveling (more than 3 months) should also consult their doctor upon their return, even if they aren't having any symptoms.

Laboratory Tests
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.

Many travelers' diseases can be identified either by culturing the microorganism, observing it under the microscope, testing for antibodies or antigens, and/or detecting the DNA or RNA of the organism.

• 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. Some bacterial stool pathogens, such as Shiga-toxin producing E. coli, can be detected by non-culture methods.
• 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 have been developed. These tests identify proteins associated with the parasite and can be useful when parasites are present in low numbers.
• 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. A rapid antigen assay also has been developed to detect the malaria parasite from a blood sample without a microscopic examination.
• 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.

Tests performed will depend on 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.

Non-Laboratory Tests
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 to discuss their travel plans and to verify that they have been vaccinated as needed and if any boosters are needed to maintain a protective level of antibodies. Since many vaccines take time to become effective or may require more than one dose, it is advised to consult with a doctor 4 to 6 weeks before departure. Many medical centers affiliated with academic universities have a Travelers' Clinic where those preparing to go abroad can obtain expert advice.

Vaccines that may be needed include:

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

For information from the Centers for Disease Control and Prevention (CDC) on vaccinations for travelers, visit their Travelers' Health web page.

If someone is traveling to areas where malaria is prevalent, the doctor will usually recommend chemoprophylaxis, such as mefloquine or chloroquine, to begin taking prior to departure. 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 CDC and the World Health Organization (WHO) have current information on travelers' diseases and strategies for prevention (see Related Content below).

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 travelers' diseases are detected and diagnosed, the easier they are to treat. Treatment will depend on the particular disease. 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.