The Burden of Illness in International Travelers
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《新英格兰医药杂志》
In 2004, 763 million people crossed international borders, reflecting an increase of 73 percent over the course of 15 years.1 International travel has rebounded since the attacks of September 11, 2001, and is steadily increasing despite a variety of global health crises, the threat of terrorism, and the war in Iraq. Nearly 55 percent of travelers are vacationing, and about 15 percent are conducting business, but a growing number are visiting friends and relatives. Typically, such travelers were born in a resource-poor country, now live in a resource-rich country, and are returning to their country of birth to visit. Moreover, though most people travel voluntarily, thousands of uncounted travelers cross borders to flee war or persecution or to seek better opportunities. During the past 25 years, a new specialty of travel medicine has evolved to address the health of these international travelers — particularly those who visit resource-poor regions. Travel to these regions carries health risks and requires preventive measures that may be unfamiliar to many physicians.
In order to fully understand the risk to an individual traveler, the physician must undertake a careful pretravel assessment, determining the person's destinations, duration of travel, planned activities, and health and immunization status. Prevention and self-treatment measures can then be matched to the traveler and the planned trip. The information about imported disease that Freedman and colleagues, drawing on data from the GeoSentinel Surveillance Network, provide in this issue of the Journal (pages 119–130) helps to define the relative risks of various illnesses according to geographic region. For example, Plasmodium falciparum malaria tends to occur in travelers to sub-Saharan Africa (particularly West Africa), dengue in visitors to the Caribbean and Southeast Asia, cutaneous leishmaniasis in those who visit Central America and South America, and typhoid fever in travelers to south central Asia. TropNetEurop, a surveillance network of experts in infectious disease and tropical medicine throughout Europe, has reported similar trends.2
(Figure)
Leg Ulcer from Leishmania.
(Figure)
Ring Forms of Plasmodium falciparum.
Courtesy of the DPDx Program, Centers for Disease Control and Prevention.
Travelers who return home with a tropical illness serve as windows into the diseases that are endemic in the countries they visited. By connecting tropical and travel medicine centers located around the world, surveillance networks document the spectrum of illness in returned travelers. This documentation enhances physicians' ability to recognize diseases that are rare in their own regions by alerting them and public health authorities to disease occurrence. Without information on the number of travelers to specific regions, the GeoSentinel surveillance data do not permit travel health advisers to determine the individual level of risk. However, they do help such professionals decide which diseases to emphasize. One clear message from the GeoSentinel data is the importance of measures that help travelers to avoid insect bites, given the frequency of vector-borne disease — malaria, dengue, leishmaniasis, and rickettsial infection — as well as the number of skin infections associated with these bites.
If all international travelers sought medical care before leaving home, and if all health care providers were well versed in the appropriate prophylactic regimens and in administering vaccines on the basis of risk, there would be much less travel-related illness. Unfortunately, probably less than half of travelers to regions with high risk for illness seek pretravel care, and many physicians make errors in judgment about measures such as malaria chemoprophylaxis and vaccines. Engaging travelers who are returning to their countries of origin for a visit is particularly difficult, since they often believe that they have little risk of contracting disease in a place that was once their home. This mistaken belief has translated into disproportionate burdens of such diseases as malaria and typhoid fever in this group of travelers.3
Even if all travelers sought health advice, however, they would still need to comply with it. For example, they would need to take their malaria chemoprophylaxis before, during, and after their trip and avoid behavior that would put them at risk for accidents, injuries, and sexually transmitted infections, including HIV infection. Data on the behavior of travelers are frequently not reassuring. Perhaps travelers would be more compliant with health recommendations if they understood the burden that diseases, such as malaria, tuberculosis, HIV infection and AIDS, and diarrheal and respiratory illnesses, have on populations in regions where the diseases are endemic.
Still, even the best-intentioned, compliant traveler cannot prevent all travel-related disease: 20 to 60 percent of visitors to resource-poor regions will have traveler's diarrhea because of widespread contamination of food and drink. Indeed, the GeoSentinel survey found a high frequency of all types of diarrhea. In addition, not all travel-related infectious disease comes from resource-poor regions: legionellosis is often associated with hotel stays in warm climates in the Mediterranean region; norovirus outbreaks, with cruise ships; and cryptosporidiosis, with exposure to water in swimming pools.
The documentation of illness in returned travelers raises several issues. First, how do we get travelers to realize that travel carries health risks and that they should seek pretravel advice from a physician or a clinic that specializes in travel medicine? As a start, we should encourage the travel industry to inform customers that health measures may need to be taken for certain destinations; we should also publicize the benefits of pretravel medical care, develop systems for providing such care specifically to travelers who visit their countries of birth, and educate physicians in the assessment of the health risks of travel.
Next, when faced with a patient, physicians need to ask, "Have you traveled abroad in the past six months?" It is important to recognize that 36 percent of travelers in the GeoSentinel survey presented with an illness a month or more after returning home. A travel history is particularly critical if the patient presents with a febrile syndrome, chronic diarrhea, or an unusual rash. A failure to associate a syndrome with travel may lead to delays in diagnosis and to adverse outcomes. Two common factors in death from malaria are a failure of the patient to take malaria chemoprophylaxis and a failure of the physician to consider the diagnosis early in the course of the illness.
Finally, although physicians do not need to be specialists in tropical medicine, they do need to be familiar with the current resources available for travel advice (see the Supplementary Appendix, available with the full text of this article at www.nejm.org) and with the most common travel-associated syndromes: those involving fever, acute and chronic diarrhea, skin disorders, and respiratory illness. Disease-specific testing needs to be performed in order to establish a diagnosis of an unusual parasitic, bacterial, or viral infection. And when physicians are uncomfortable making a diagnosis, they need to refer the patient to a specialist.
Given the increasing number of travelers with tropical diseases who are returning to Western regions and the heavy burden of disease in resource-poor regions, there is a clear need for continued education and training in tropical medicine, as well as for the development and supply of effective medications and vaccines. As more and more informed travelers receive pretravel health care and informed physicians increasingly consider the travel history when caring for ill returned travelers, international travel should become a healthier experience.
Source Information
Dr. Hill is the director of the National Travel Health Network and Center and an honorary professor at the London School of Hygiene and Tropical Medicine — both in London.
References
WTO tourism highlights, edition 2005. Madrid: World Tourism Organization, 2005:1-12. (Accessed December 21, 2005, at http://www.world-tourism.org/facts/menu.html.)
Jelinek T, Mühlberger N. Surveillance of imported diseases as a window to travel health risks. Infect Dis Clin North Am 2005;19:1-13.
Bacaner N, Stauffer B, Boulware DR, Walker PF, Keystone JS. Travel medicine considerations for North American immigrants visiting friends and relatives. JAMA 2004;291:2856-2864.(David R. Hill, M.D., D.T.)
In order to fully understand the risk to an individual traveler, the physician must undertake a careful pretravel assessment, determining the person's destinations, duration of travel, planned activities, and health and immunization status. Prevention and self-treatment measures can then be matched to the traveler and the planned trip. The information about imported disease that Freedman and colleagues, drawing on data from the GeoSentinel Surveillance Network, provide in this issue of the Journal (pages 119–130) helps to define the relative risks of various illnesses according to geographic region. For example, Plasmodium falciparum malaria tends to occur in travelers to sub-Saharan Africa (particularly West Africa), dengue in visitors to the Caribbean and Southeast Asia, cutaneous leishmaniasis in those who visit Central America and South America, and typhoid fever in travelers to south central Asia. TropNetEurop, a surveillance network of experts in infectious disease and tropical medicine throughout Europe, has reported similar trends.2
(Figure)
Leg Ulcer from Leishmania.
(Figure)
Ring Forms of Plasmodium falciparum.
Courtesy of the DPDx Program, Centers for Disease Control and Prevention.
Travelers who return home with a tropical illness serve as windows into the diseases that are endemic in the countries they visited. By connecting tropical and travel medicine centers located around the world, surveillance networks document the spectrum of illness in returned travelers. This documentation enhances physicians' ability to recognize diseases that are rare in their own regions by alerting them and public health authorities to disease occurrence. Without information on the number of travelers to specific regions, the GeoSentinel surveillance data do not permit travel health advisers to determine the individual level of risk. However, they do help such professionals decide which diseases to emphasize. One clear message from the GeoSentinel data is the importance of measures that help travelers to avoid insect bites, given the frequency of vector-borne disease — malaria, dengue, leishmaniasis, and rickettsial infection — as well as the number of skin infections associated with these bites.
If all international travelers sought medical care before leaving home, and if all health care providers were well versed in the appropriate prophylactic regimens and in administering vaccines on the basis of risk, there would be much less travel-related illness. Unfortunately, probably less than half of travelers to regions with high risk for illness seek pretravel care, and many physicians make errors in judgment about measures such as malaria chemoprophylaxis and vaccines. Engaging travelers who are returning to their countries of origin for a visit is particularly difficult, since they often believe that they have little risk of contracting disease in a place that was once their home. This mistaken belief has translated into disproportionate burdens of such diseases as malaria and typhoid fever in this group of travelers.3
Even if all travelers sought health advice, however, they would still need to comply with it. For example, they would need to take their malaria chemoprophylaxis before, during, and after their trip and avoid behavior that would put them at risk for accidents, injuries, and sexually transmitted infections, including HIV infection. Data on the behavior of travelers are frequently not reassuring. Perhaps travelers would be more compliant with health recommendations if they understood the burden that diseases, such as malaria, tuberculosis, HIV infection and AIDS, and diarrheal and respiratory illnesses, have on populations in regions where the diseases are endemic.
Still, even the best-intentioned, compliant traveler cannot prevent all travel-related disease: 20 to 60 percent of visitors to resource-poor regions will have traveler's diarrhea because of widespread contamination of food and drink. Indeed, the GeoSentinel survey found a high frequency of all types of diarrhea. In addition, not all travel-related infectious disease comes from resource-poor regions: legionellosis is often associated with hotel stays in warm climates in the Mediterranean region; norovirus outbreaks, with cruise ships; and cryptosporidiosis, with exposure to water in swimming pools.
The documentation of illness in returned travelers raises several issues. First, how do we get travelers to realize that travel carries health risks and that they should seek pretravel advice from a physician or a clinic that specializes in travel medicine? As a start, we should encourage the travel industry to inform customers that health measures may need to be taken for certain destinations; we should also publicize the benefits of pretravel medical care, develop systems for providing such care specifically to travelers who visit their countries of birth, and educate physicians in the assessment of the health risks of travel.
Next, when faced with a patient, physicians need to ask, "Have you traveled abroad in the past six months?" It is important to recognize that 36 percent of travelers in the GeoSentinel survey presented with an illness a month or more after returning home. A travel history is particularly critical if the patient presents with a febrile syndrome, chronic diarrhea, or an unusual rash. A failure to associate a syndrome with travel may lead to delays in diagnosis and to adverse outcomes. Two common factors in death from malaria are a failure of the patient to take malaria chemoprophylaxis and a failure of the physician to consider the diagnosis early in the course of the illness.
Finally, although physicians do not need to be specialists in tropical medicine, they do need to be familiar with the current resources available for travel advice (see the Supplementary Appendix, available with the full text of this article at www.nejm.org) and with the most common travel-associated syndromes: those involving fever, acute and chronic diarrhea, skin disorders, and respiratory illness. Disease-specific testing needs to be performed in order to establish a diagnosis of an unusual parasitic, bacterial, or viral infection. And when physicians are uncomfortable making a diagnosis, they need to refer the patient to a specialist.
Given the increasing number of travelers with tropical diseases who are returning to Western regions and the heavy burden of disease in resource-poor regions, there is a clear need for continued education and training in tropical medicine, as well as for the development and supply of effective medications and vaccines. As more and more informed travelers receive pretravel health care and informed physicians increasingly consider the travel history when caring for ill returned travelers, international travel should become a healthier experience.
Source Information
Dr. Hill is the director of the National Travel Health Network and Center and an honorary professor at the London School of Hygiene and Tropical Medicine — both in London.
References
WTO tourism highlights, edition 2005. Madrid: World Tourism Organization, 2005:1-12. (Accessed December 21, 2005, at http://www.world-tourism.org/facts/menu.html.)
Jelinek T, Mühlberger N. Surveillance of imported diseases as a window to travel health risks. Infect Dis Clin North Am 2005;19:1-13.
Bacaner N, Stauffer B, Boulware DR, Walker PF, Keystone JS. Travel medicine considerations for North American immigrants visiting friends and relatives. JAMA 2004;291:2856-2864.(David R. Hill, M.D., D.T.)