Carlos Franco-Paredes
There are no official CDC guidelines or recommendations for screening of asymptomatic international travelers, except in special populations such as refugees at the time of their initial domestic evaluation. Cost-effectiveness studies of routine screening in asymptomatic international travelers have not shown a significant benefit to this approach on a population basis. Therefore, a clinic visit or any nonfocused laboratory screening for the majority of travelers is not indicated. Exceptions would be for those with known high-risk exposures that are linked to the transmission of certain agents.
The decision to screen for particular pathogens will depend on the type of travel, itinerary, and exposure history.
- Travelers who have engaged in casual unprotected sex or have received an injection, a body piercing, or a tattoo may be screened for HIV, hepatitis B and C, and potentially transmitted sexually transmitted diseases (such as gonorrhea) with nucleic acid hybridization tests in urine, and for Chlamydia infections with nucleic acid amplification tests in urine. Sometimes testing for hepatitis B DNA or hepatitis C RNA viral load and HIV RNA viral load is recommended for travelers with high-risk factors presenting with a febrile illness, in order to rule out the possibility of acute hepatitis B or C or an acute HIV syndrome, respectively.
- Travelers who have been exposed to freshwater in areas endemic for schistosomiasis should be screened for this infection by serology and stool or urine tests, or both. Travelers exposed to soil should be screened for strongyloidiasis and possibly other intestinal parasites. Eosinophilia in a returned traveler suggests the possibility of a helminth infection, of which the most important is strongyloidiasis. If left untreated, this infection may last for the lifetime of the host, and in an immunocompromised person it has the potential to disseminate.
- Travelers who resided in poorly constructed dwellings in highly endemic areas for American trypanosomiasis (Chagas disease) should be serologically screened for latent Trypanosoma cruzi infection.
- Asymptomatic international travelers who have been abroad for many months or longer, particularly in resource-limited settings, should be screened for certain diseases, using tests such as hepatitis B serology, HIV serology, syphilis serology, Mantoux intradermal skin test for latent tuberculosis infection (pre-departure baseline skin testing is recommended in long-term travelers visiting resource-limited settings), stool examination for ova and parasites, and complete blood count, including a peripheral eosinophil count and red blood cell parameters.
Asymptomatic screening is encouraged in special populations such as refugees or international adoptees.
- Some of the frequently recommended tests to conduct in these patient groups include—
- Hepatitis B serologic panel
- HIV serology
- Syphilis serology
- Complete blood count, including a peripheral eosinophil count and red blood cell parameters
- Screening for latent tuberculosis infection can be performed by using one of two modalities: the Mantoux tuberculin skin test (TST) or a blood assay for Mycobacterium tuberculosis infection. Currently, the QuantiFERON-TB Gold In-tube Test (QFT-G) is approved for such purposes in the United States in adults. Chest radiograph and sputum studies for mycobacterial staining should be performed for those with positive screening results.
CDC has published guidelines for evaluating refugees for intestinal parasites and tissue-invading parasites during domestic medical evaluations. Screening modalities vary according to predeparture presumptive parasitic therapy:
- Screening for parasitic infection among asymptomatic refugees who had no documented predeparture presumptive antiparasitic therapy should include two morning stool samples for ova and parasite examination by the concentration method.
- Screening for parasitic infection among asymptomatic refugees who received single-dose predeparture treatment with albendazole should include the following:
- An eosinophil count should be performed in every refugee.
- Those from Sub-Saharan Africa with persistent eosinophilia should undergo serologic testing for strongyloidiasis and schistosomiasis.
- Screening for parasitic infection among asymptomatic refugees who received high-dose predeparture albendazole (7-day therapy) or ivermectin, with or without praziquantel should include a follow-up eosinophil count 3–6 months after antiparasitic treatment is suggested for those identified with residual eosinophilia at the initial evaluation.
Further screening and testing guidelines are expected to be issued by the CDC in the near future that will make screening for refugees more uniform and help tailor evaluations to specific populations. These guidelines will be accessible on the CDC website at www.cdc.gov/yellowbook/RefugeeGuidelines.
