An estimated 1 billion people will travel internationally in 2012, some of whom are immunocompromised hosts and who are more vulnerable to infection and subsequent complications, including those with cancer, human immunodeficiency virus/acquired immune deficiency syndrome, organ transplant recipients, or those on immunosuppressive drugs for autoimmune disorders. Little is known about the risks of travel in immunocompromised hosts. There are a handful of descriptive studies on travel medicine in organ transplant[2-4] and splenectomized patients, although larger studies are yet to be done.
Mikati and colleagues describe the first retrospective cohort study of cancer patients who presented for pre-travel health advice at a single center over an 8-year span. They describe and compare the international travel patterns, infectious diseases exposure risks, pre-travel interventions, and travel-related illnesses in 149 subjects with solid tumors, hematological malignancies, and stem cell transplantation. Those with impaired immunity had similar infectious diseases exposure risks and travel patterns compared with the control group of travelers whose cancer was cured or in remission. Furthermore, most of the reported travel-related illnesses were of minor nature. Based on the retrospective nature of the study, and the fact that subjects might not have returned or reported back to their cancer center with travel-related illness, they may have missed some amount of travel-related illness. Nonetheless, this is the largest published study examining travel patterns and infectious diseases exposure risks of patients diagnosed with cancer. Additional prospective studies would be helpful to determine the rate of international travel, travel-related vaccine effectiveness, and travel-related illnesses in cancer patients. Such data is crucial in developing clinical and research programs to deliver better protection to immunocompromised hosts wishing to travel.
Surveys of solid organ transplant (SOT) recipients document insufficient rates of pre-travel counseling and interventions. In one Canadian survey of 267 SOT recipients, 95 (36%) had recently traveled outside Canada and the United States, and many recommended preventive measures were overlooked. For example, 63% had traveled to areas endemic for hepatitis A, yet only 5% had received hepatitis A immunization; 50% traveled to dengue- and malaria-endemic areas, although only 25% adhered to mosquito prevention measures; and 10% reported behaviors that exposed them to blood or body fluids. A review at the Mayo Clinic, Rochester, Minnesota found that 303 (27%) of 1,130 SOT recipients had traveled abroad; 96% did not seek pre-travel healthcare, and 8% had illness requiring medical attention. In a Dutch study of 290 Dutch kidney transplant recipients, 34% had traveled outside Western Europe and Northern America; 22% of these travelers did not seek pre-travel health advice and 29% were ill during their most recent journey, with 24% of ill travelers needing hospitalization for their illness. The majority of Canadian and Dutch SOT recipients were apt to consult their transplant physician for pre-travel advice. Taken together, these studies suggest a need for better pre-travel education and preventative measures in immunocompromised hosts. Guidelines for travel medicine in SOT recipients help guide clinical care.
A travel medicine specialist familiar with their immunocompromised status and medications should see such patients who wish to travel. Immunocompromised hosts may respond less to vaccination, and may be less protected from disease. Furthermore, some live vaccines are contraindicated in immunocompromised hosts, including measles, mumps, rubella, varicella/zoster, yellow fever, smallpox, Bacillus Calmette–Guérin (BCG), and oral typhoid fever vaccines; unprotected immunocompromised hosts should be warned about the risks of travel to areas of significant disease activity. For yellow fever regions, they should usually be given a yellow fever vaccine waiver letter stating that the contraindication to vaccination is acceptable to most governments; such letters should bear the stamp of an official, approved yellow fever immunization center. While some less immunosuppressed travelers have tolerated the vaccine, including individuals with a distant history of hematological malignancy,[8, 9] complications including death have been reported in immunosuppressed individuals after vaccination and recommendations avoid its use in immunocompromised travelers. The findings of Mikati and colleagues that immunocompetent travelers were more likely to visit regions endemic for yellow fever than immunocompromised travelers (22% vs 11%, p = 0.07) may reflect education steering them away from these zones.
Practitioners caring for immunocompromised hosts may find the following sites useful in providing country-specific information that may assist with preliminary information: for example, the Centers for Disease Control and Prevention Travelers' Health site (wwwnc.cdc.gov/travel/destinations/list.htm), the World Health Organization (www.who.int/ith/chapters/en/index.html), or MD Travel Health (www.mdtravelhealth.com). A new book on travel medicine for patients has a special section on travel medicine for immunocompromised hosts.
Clinicians should be aware that patients may return with unexpected pathogens, including both geographically restricted illnesses (ie, dengue and hepatitis E), and also routine but more resistant pathogens (ie, multidrug-resistant Salmonella and extended-spectrum beta-lactamase producing organisms). Lastly, certain diseases may especially affect immunocompromised hosts even years later. Leishmaniasis can alter the presentation, diagnosis, and course of various malignant disorders. Other pathogens can reactivate in the setting of immunosuppression, ie Mycobacterium tuberculosis and Strongyloides stercoralis, and chemoprophylaxis should be given to those shown to have (or at high risk for) latent infection before starting immunosuppressive drugs.
The importance of both prevention via pre-travel medicine and a detailed travel history remains crucial in providing optimal care.