Approach to Travel Medicine and Contents of a Personal Travel Medicine Kit

Immunizations for Travel

Travelers going to destinations in tropical and developing countries from countries in North America and Western Europe are exposed to communicable diseases that are infrequently encountered at home due to a generally high standard of sanitation and mandatory childhood immunization programs. For example, adult travelers have acquired measles and chickenpox on trips abroad. Paralytic polio is transmitted outside the Western Hemisphere in countries where sanitary conditions favor oral-fecal transmission and routine immunizations do not reach a high level of coverage among susceptible populations. Thus all travelers should be questioned about their status with regard to the routine immunizations of childhood—tetanus, diphtheria, measles, mumps, rubella, and polio—and a primary series or booster doses of the vaccines should be given as appropriate. Vaccines against Haemophilus influenzae type b, hepatitis A, hepatitis B, human papillomavirus, meningococcal disease, pertussis, pneumococcal disease, and varicella are also included in the current childhood and pre-adolescent immunization schedules in the United States. Older children and adult travelers should be up-to-date with age-appropriate booster doses or receive a primary series of these standard immunizations if travel will place them at risk ( Chapter 5 ). Travel immunizations for children are covered in Chapter 12 .

The vaccinations administered to travelers should be recorded in a copy of the yellow booklet, the “International Certificate of Vaccination or Prophylaxis,” which is recognized by the WHO. This record should be kept in a secure place with the passport, as it becomes a lifelong immunization record. There is a special page for validation of the yellow fever vaccine, which must be done in an official vaccination center, as well as additional pages to record the other vaccines.

Up-to-date information on areas where cholera and yellow fever are reported is best obtained from the CDC ( www.cdc.gov/travel ) or the WHO ( www.who.int ) websites. Smallpox and cholera vaccines are no longer required for international travel, according to WHO regulations. Proof of meningococcal vaccine receipt is required for visa applications to Saudi Arabia during the time of the Hajj. In the United States, owing to relatively limited supplies and the fact that it must be given within 1 hour after reconstitution of the vaccine, the yellow fever vaccine is available only from official vaccination centers registered by the Department of Public Health in each state.

Some confusion exists over the difference between required vaccinations and recommended vaccinations. In the CDC publication Health Information for International Travel (commonly called “The Yellow Book”), there is a country-by-country listing of vaccines required for entry. The Yellow Book can be accessed through the CDC website or purchased in printed format. Someone calling a travel clinic to ask which shots are required for a trip to Kenya or Venezuela, for instance, would be told by staff consulting the Yellow Book that yellow fever vaccine is not required for a traveler arriving from North America. Yet if one refers to maps showing where yellow fever is endemic, one can see that Kenya and Venezuela both lie within the endemic zones. Thus, yellow fever vaccine might be recommended to a traveler to those countries even though the vaccine is not a requirement for entry, depending on that traveler's intended activities and in-country itinerary.

Other vaccines may be recommended to travelers, depending on their destinations, degree of rural exposure during travel, eating habits, purpose of the trip, and state of health. In this group are the vaccines against hepatitis A, typhoid fever, cholera, meningococcal disease, rabies, Japanese encephalitis, and influenza. Certain travelers, such as healthcare workers, missionaries, Peace Corps volunteers, students, and any person likely to have household or sexual contact with residents in tropical or developing countries should consider immunization against hepatitis B. Persons who are going to tour rural areas or live or work in the People's Republic of China, India, Thailand, Republic of Korea, and other Asian countries need to consider Japanese encephalitis B vaccine. Travel immunizations are considered in detail in Chapter 5 .

Malaria Chemoprophylaxis

In addition to travel immunizations, a major consideration for international travelers is whether their travel will take them to an area where malaria is transmitted. Malaria has a worldwide distribution in tropical and subtropical areas. It is reemerging in areas once considered to be free from risk and continues to be a serious problem for the traveler because of the emergence of new drug-resistant strains in areas where the use of chloroquine phosphate and other antimalarial drugs were formerly highly effective for malaria prevention and treatment.

In Africa, South America, Asia, and the South Pacific, infections with chloroquine-resistant Plasmodium falciparum malaria (CRPF) are a significant risk to travelers because falciparum malaria can rapidly progress to serious morbidity and mortality if not promptly diagnosed and treated. Updated information on the risk of CRPF is published in the CDC publication Morbidity and Mortality Weekly Report , but the CDC website should be consulted for the most current information on a given travel destination. Chemoprophylaxis, or the taking of drugs to prevent clinical attacks of malaria, is recommended to travelers going to areas of malaria transmission, in addition to personal insect precautions. Drugs currently used for the prevention of chloroquine-resistant malaria include mefloquine (Larium®), doxycycline (Doryx®, Vibramycin®), and atovaquone/proguanil (Malarone®). These and other antimalarial drugs are discussed in Chapters 6 and 20 .

Malaria is a protozoan parasite transmitted to humans by nighttime biting female anopheline mosquitoes. Since the risk of infection is related to the number of bites sustained, and since current malaria chemoprophylaxis regimens are not completely protective, all travelers should follow certain simple precautions when visiting or staying in malarious areas ( Tables 1.3 and 1.4 ). In addition to preventing bites from mosquitoes spreading malaria, these precautions will help the traveler avoid bites from other mosquito species and insects that spread a variety of diseases in tropical and subtropical areas, for which there are no prophylactic drugs nor vaccines (dengue fever, hemorrhagic fevers, viral encephalitis, leishmaniasis, trypanosomiasis, filariasis, etc.) ( Table 1.5 ). In an analysis of travel-associated illnesses among 17,353 returned travelers reporting to a GeoSentinel Site by Freedman and co-authors, vector-borne diseases accounted for almost 40% of the case reports, exceeding respiratory transmitted diseases and food- and water-borne diseases, respectively.

Traveler's Diarrhea

Between 30 and 60% of travelers to tropical countries are affected by traveler's diarrhea. This illness is characterized by sudden onset of four to five movements of watery diarrhea per day, sometimes accompanied by abdominal cramps, malaise, nausea, and vomiting. An attack typically lasts 3-6 days. The pathogens causing gastrointestinal disease are acquired mostly through fecal-oral contamination, and preventive strategies to avoid illness include careful selection of food and water ( Chapter 8 ).

Adequate means for purification of water vary depending on the water source. Bringing water to a boil is probably the most reliable way to kill pathogens up to 20,000 ft above sea level. Water purification tablets are convenient and commercially available, and are almost as effective as boiling when the water is at 68° F (20° C). Portable water purification filters have become a popular alternative employed by many travelers; the devices using iodine–resin technology have proved to be effective against the broadest range of pathogens. Heating, chemical, and filtration methods of water purification are discussed in detail in Chapter 7 .

Owing to widespread publicity in the lay press, many travelers want to know more about the use of antibiotics to prevent diarrhea while traveling. Most travel health experts advise against using drugs as a preventive measure for traveler's diarrhea, the chief objections being the potential for undesirable side effects, allergic reactions, and possible occurrence of antibiotic-associated colitis. However, in selected travelers with time-sensitive mission-critical objectives, prevention of traveler's diarrhea might warrant the use of antibiotic prophylaxis involving daily oral doses of antibiotics for a limited time. Antibiotic prophylaxis and empiric self-treatment of traveler's diarrhea are discussed in detail in Chapter 8 .