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A new medical specialty, travel medicine, emerged in the 1980s in response to the health needs of increasing numbers of international travelers—a phenomenon resulting from the rapid expansion and growing accessibility of commercial jet transportation. In 1990, the World Tourism Organization (WTO) reported approximately 457 million international arrivals per year. In 2014, the WTO reported 1138 million international arrivals per year, and just under half of these involved countries outside Europe. The upward trend in international travel is projected to continue.
When travel involves geographic translocations of people going from relatively sanitary and industrialized countries in northern temperate zones to destinations in countries with developing economies and tropical environments, potential exposures to exotic diseases and exacerbations of chronic health conditions during travel create unique health concerns for both individuals and societies. Travel medicine is interdisciplinary: it involves a spectrum of knowledge across the health specialties of epidemiology, preventive medicine, primary care, emergency medicine, infectious diseases, tropical medicine, gastroenterology, dermatology, and others. Travel health providers apply a heightened geographic awareness of destination-specific diseases and environmental conditions, as well as considerations of personal safety and well-being to individuals and their journeys.
As international travelers pursue their exploration of the world for recreational, educational, business, religious, and humanitarian purposes, physicians and other healthcare providers need to know how to counsel their traveling patients with regard to a wide variety of health issues. It has been reported that only 1-3.6% of deaths in travelers are due to infectious diseases; however, the risks for acute and chronic morbidity in the individual traveler and the potential for global spread of common as well as exotic human pathogens means that continued attention to transmission, treatment, prevention, and control of communicable diseases are essential considerations for international travelers ( Chapter 3, Chapter 4, Chapter 5, Chapter 6, Chapter 7, Chapter 8, Chapter 9 ). Travel health issues involving environmental factors, from time zone changes to air pollution, temperature extremes, and barometric influences at high altitude and undersea are covered in Chapter 2, Chapter 9, Chapter 10, Chapter 11 . The psychological and emotional well-being of international travelers is increasingly recognized as a factor contributing to travelers' health ( Chapters 2 and 17 ).
Personal safety has emerged as another important issue in travelers' health. Studies have shown that motor vehicle accidents (25%) and other injuries and accidents (15%, including drownings and falls from height) accounted for more deaths in American travelers than infectious diseases and other illnesses (10%). Heart attacks and other cardiovascular problems in male travelers over 60 years of age accounted for 50% of reported deaths but probably do not represent a preventable consequence of travel. Recommendations for travelers with special needs are given in Chapter 12, Chapter 13, Chapter 14, Chapter 15, Chapter 16, Chapter 17, Chapter 18, Chapter 19 .
Travel medicine practice involves the “travel medicine triad” consisting of the traveler, the trip, and the proposed health interventions ( Fig. 1.1 ). The health status of the traveler is the starting point: the very young and the very old are at increased risk from certain infectious diseases due to age-related changes in the immune system; travelers with underlying medical conditions may need more assistance in the health maintenance strategies during travel and may even need to alter their desired itineraries based on access to healthcare at the destination.
Assessment of trip risks is related to the destination(s), with travel to rural tropical areas, communities with high prevalence or outbreaks of diseases that are not preventable by vaccine, extreme environments, and remote regions presenting more challenges than trips on standard tourist routes. Updated information on outbreaks, epidemics, and health conditions abroad are posted on the websites of the Centers for Disease Control and Prevention (CDC, www.cdc.gov ) in Atlanta, Georgia, and the World Health Organization (WHO, www.who.int ) in Geneva, Switzerland. In addition to the CDC and WHO, regional health agencies and public and private health information services also issue periodic guidelines and health information for international travelers. However, many guidelines are by necessity very general; the optimal practice of travel medicine calls for individualized recommendations for each traveler and trip based on the travel health assessment described by the “travel medicine triad” above. Whenever possible, international travelers should seek medical advice 4-6 weeks in advance of their departure date. This allows adequate time for immunizations to be scheduled, for advice and prescriptions to be given, and for special information to be obtained when needed .
The medical approach to travel becomes even more complex when the traveler plans a long-term trip lasting months to years, often involving multiple destinations. Such travelers may need to start 3 or more months in advance of anticipated trip departure in order to complete vaccine series and other health examinations needed for issuance of visas, permits, school registrations, and other required documents. Table 1.1 summarizes the steps for pre-travel medical preparation.
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All travelers should be advised to assemble the information listed in Table 1.2 in a concise and clearly written form to carry with them. In addition, travelers should plan to carry a supply of medications adequate to last the duration of the trip in their carry-on (not checked) luggage and an extra pair of eyeglasses even if contact lenses are usually worn, along with a copy of the prescription for the corrective lenses.
International travelers should assemble the following information in a concise and clearly written form to carry with them:
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Health interventions in travel clinics include health education on the trip risks identified for a particular traveler and trip and, at a minimum, recommendations on immunizations, malaria chemoprophylaxis, management of traveler's diarrhea, and prevention of insect-vectored diseases.
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 .
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.
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Examples of Insect Repellents Containing DEET for Skin Application
Examples of Permethrin-Containing Insecticides for Application to External Clothing and Mosquito Nets (see Fig. 1.2 )
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a Brand names are given for identification purposes only and do not constitute an endorsement.
Arthropod Vector | Biting Characteristics | Disease |
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Anopheles mosquitoes |
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Aedes mosquitoes |
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Culex mosquitoes |
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Mansonia mosquitoes |
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Fleas |
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Body lice |
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Ticks |
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Mites |
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Culicoides midges (no-see-ums) |
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Mansonellosis |
Deer and horseflies (Tabanids) |
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Black flies ( Simulium ) |
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Onchocerciasis (river blindness) |
Sandflies ( Phlebotomus , Lutzomyia ) |
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Tsetse flies ( Glossina ) |
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Triatomine/reduviid bugs |
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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 .
Emergency medical care abroad is not a subject likely to be broached by the average travel agent, for fear of alarming the potential traveler. Yet all travelers, especially those planning long-term travel (trips of 3 weeks or longer), the very young and the very old, and those with special medical conditions (cardiac, pulmonary, gastrointestinal, or hematologic problems; pregnancy; human immunodeficiency virus [HIV] infection; organ transplant; etc.) need to have a plan in case the need for emergency medical care arises. Even the young traveler in perfect health can break a leg, be involved in a motor vehicle accident, or be bitten by a rabid dog.
People planning trips to exotic places but who will stay in urban, first-class hotels may have relatively easy access to English-speaking physicians with biomedical training at a level seen in high-income nations. However, many places where modern tourists go are far from English-speaking medical practitioners and modern hospitals. At some travel destinations, medications for treatment of certain infections and special medical conditions may not be available under any circumstances. Thus, for such travelers, pre-travel counseling, preparation of the traveler's medical kit, and a medical emergency evacuation plan are of great importance.
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