Screening Asymptomatic Returned Travelers

Screening Asymptomatic Returned Travelers is a topic covered in the CDC Yellow Book.

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CDC has no official guidelines or recommendations for screening asymptomatic international travelers without other specific risk factors. (For recommendations regarding the screening of newly arrived immigrants and refugees, see Newly Arrived Immigrants & Refugees in this chapter.) Nevertheless, the screening of travelers returning from developing countries represents a substantial portion of the activity of many travel and tropical medicine clinics.

The scientific literature on the cost effectiveness of screening asymptomatic travelers is sparse. It is clear that asymptomatic travelers can harbor many infections acquired during travel, some of which have the potential to cause serious sequelae or have public health implications. In some cases, these will include pathogens rarely found in the traveler’s country of origin. US medical practitioners may have little familiarity with the associated diseases, and specific diagnostic tests may not be readily available or may have poorly defined operating characteristics.

The decision to screen for particular pathogens partly will depend on the type of travel, itinerary, and exposure history. Screening short-term healthy travelers who do not report a particular exposure is often not necessary. On the other hand, special groups of travelers such as long-term travelers (expatriates, aid workers, and missionaries), travelers visiting friends and relatives, and adventure travelers may have prolonged or heavy exposure to particular pathogens, and specific tests may be considered. Clinicians should be aware that exposure history may be unreliable and may not be predictive of infection. Further, the value of a detailed itinerary can be limited by incomplete information on where pathogens are endemic. Finally, the type of travel may not provide a practical assessment of risk.

Screening traditionally has been viewed as a secondary prevention intervention, that is, an attempt to identify existing occult illnesses or health risks. The cost effectiveness of screening is dependent on the disease of interest and involves several considerations. Before screening asymptomatic travelers, the physician should evaluate the potential outcomes associated with the disease and whether an early intervention may reduce morbidity or mortality.

Evaluate screening tests with respect to sensitivity and specificity, risk to the patient, and cost. The low prevalence of tropical infections in asymptomatic travelers will heavily influence the positive predictive value of the screening tests, leading to an increased likelihood of false-positive results. As a result, the asymptomatic traveler may be subjected to further investigations, generating higher costs, anxiety, and possible other harms related to diagnostic followup, and creating complex considerations when balancing risks and benefits.

Because of convenience and patient susceptibility to suggestion at the time of screening, the screening visit may offer an opportunity to promote primary prevention by discussing behavioral or other risk factors predisposing to ill health, such as exposure to contaminated food and water, arthropods, and fresh water, and behavioral risks such as drug use or high-risk sex. For many long-term travelers, visits for asymptomatic screening may also be their only hiatus from a continuing assignment abroad that allows for a general health evaluation. The usual recommendations for the periodic health exam, which may include screening for hypertension, diabetes, cardiovascular disorders, and malignancy, would apply. These visits also provide an opportunity to review vaccination status, malaria prophylaxis, and health behaviors.

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CDC has no official guidelines or recommendations for screening asymptomatic international travelers without other specific risk factors. (For recommendations regarding the screening of newly arrived immigrants and refugees, see Newly Arrived Immigrants & Refugees in this chapter.) Nevertheless, the screening of travelers returning from developing countries represents a substantial portion of the activity of many travel and tropical medicine clinics.

The scientific literature on the cost effectiveness of screening asymptomatic travelers is sparse. It is clear that asymptomatic travelers can harbor many infections acquired during travel, some of which have the potential to cause serious sequelae or have public health implications. In some cases, these will include pathogens rarely found in the traveler’s country of origin. US medical practitioners may have little familiarity with the associated diseases, and specific diagnostic tests may not be readily available or may have poorly defined operating characteristics.

The decision to screen for particular pathogens partly will depend on the type of travel, itinerary, and exposure history. Screening short-term healthy travelers who do not report a particular exposure is often not necessary. On the other hand, special groups of travelers such as long-term travelers (expatriates, aid workers, and missionaries), travelers visiting friends and relatives, and adventure travelers may have prolonged or heavy exposure to particular pathogens, and specific tests may be considered. Clinicians should be aware that exposure history may be unreliable and may not be predictive of infection. Further, the value of a detailed itinerary can be limited by incomplete information on where pathogens are endemic. Finally, the type of travel may not provide a practical assessment of risk.

Screening traditionally has been viewed as a secondary prevention intervention, that is, an attempt to identify existing occult illnesses or health risks. The cost effectiveness of screening is dependent on the disease of interest and involves several considerations. Before screening asymptomatic travelers, the physician should evaluate the potential outcomes associated with the disease and whether an early intervention may reduce morbidity or mortality.

Evaluate screening tests with respect to sensitivity and specificity, risk to the patient, and cost. The low prevalence of tropical infections in asymptomatic travelers will heavily influence the positive predictive value of the screening tests, leading to an increased likelihood of false-positive results. As a result, the asymptomatic traveler may be subjected to further investigations, generating higher costs, anxiety, and possible other harms related to diagnostic followup, and creating complex considerations when balancing risks and benefits.

Because of convenience and patient susceptibility to suggestion at the time of screening, the screening visit may offer an opportunity to promote primary prevention by discussing behavioral or other risk factors predisposing to ill health, such as exposure to contaminated food and water, arthropods, and fresh water, and behavioral risks such as drug use or high-risk sex. For many long-term travelers, visits for asymptomatic screening may also be their only hiatus from a continuing assignment abroad that allows for a general health evaluation. The usual recommendations for the periodic health exam, which may include screening for hypertension, diabetes, cardiovascular disorders, and malignancy, would apply. These visits also provide an opportunity to review vaccination status, malaria prophylaxis, and health behaviors.

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