Chapter 117. Health Advice for International Travel (Part 7) Gastrointestinal Illness Decreased levels of gastric acid, abnormal gastrointestinal mucosal immunity, other complications of HIV infection, and medications taken by HIV- infected patients make travelers' diarrhea especially problematic in these individuals. Travelers' diarrhea is likely to occur more frequently, be more severe, be accompanied by bacteremia, and be more difficult to treat. Although uncommon, Cryptosporidium, Isospora belli, and Microsporidium infections are associated with increased morbidity and mortality in AIDS patients. The HIV-infected traveler must be careful to consume only appropriately prepared foods and beverages and may benefit from antibiotic prophylaxis for travelers' diarrhea. Sulfonamides (as used to prevent pneumocystosis) are ineffective because of widespread resistance. Other Travel-Related Infections Data are lacking on the severity of many vector-borne diseases in HIV- infected individuals. Malaria is especially severe in asplenic persons and in those with AIDS. The HIV load doubles during malaria, with subsidence in ~8–9 weeks; the significance of this increase in viral load is unknown. Visceral leishmaniasis (Chap. 205) has been reported in numerous HIV- infected travelers. Diagnosis may be difficult, given that splenomegaly and hyperglobulinemia are often lacking and serologic results are frequently negative. Sandfly bites may be prevented by evening use of insect repellents. Certain respiratory illnesses, such as histoplasmosis and coccidioidomycosis, cause greater morbidity and mortality among patients with AIDS. Although tuberculosis is common among HIV-infected persons (especially in developing countries), its acquisition by the short-term HIV-infected traveler has not been reported as a major problem. Medications Adverse events due to medications and drug interactions are common and raise complex issues for HIV-infected persons. Rates of cutaneous reaction (e.g., increased cutaneous sensitivity to sulfonamides) are unusually high among patients with AIDS. Since zidovudine is metabolized by hepatic glucuronidation, inhibitors of this process may elevate serum levels of the drug. Concomitant administration of the antimalarial drug mefloquine and the antiretroviral agent ritonavir may result in decreased plasma levels of ritonavir. In contrast, no significant influence of concomitant mefloquine administration on plasma levels of indinavir or nelfinavir was detected in two HIV-infected travelers. There is a strong theoretical concern that the antimalarial drugs lumefantrine (combined with artemisinin in Coartem and Riamet) and halofantrine may interact with HIV protease inhibitors and nonnucleoside reverse transcriptase inhibitors since the latter are known to be potent inhibitors of cytochrome P450. Chronic Illness, Disability, and Travel Chronic health problems need not prevent travel, but special measures can make the journey safer and more comfortable. Heart Disease Cardiovascular events are the main cause of deaths among travelers and of in-flight emergencies on commercial aircraft. Extra supplies of all medications should be kept in carry-on luggage, along with a copy of a recent electrocardiogram and the name and telephone number of the traveler's physician at home. Pacemakers are not affected by airport security devices, although electronic telephone checks of pacemaker function cannot be transmitted by international satellites. Travelers with electronic defibrillators should carry a note to that effect and ask for hand screening. A traveler may benefit from supplemental oxygen; since oxygen delivery systems are not standard, supplementary oxygen should be ordered by the traveler's physician well before flight time. Travelers may benefit from aisle seating and should walk, perform stretching and flexing exercises, consider wearing support hose, and remain hydrated during the flight to prevent venous thrombosis and pulmonary embolism. Chronic Lung Disease Chronic obstructive pulmonary disease is one of the most common diagnoses in patients who require emergency-department evaluation for symptoms occurring during airline flights. The best predictor of the development of in-flight problems is the sea-level Pa O2 . A Pa O2 of at least 72 mmHg corresponds to an in- flight arterial Pa O2 of ~55 mmHg when the cabin is pressurized to 2500 m (8000 ft). If the traveler's baseline Pa O2 is <72 mmHg, the provision of supplemental oxygen should be considered. Contraindications to flight include active bronchospasm, lower respiratory infection, lower-limb deep-vein phlebitis, pulmonary hypertension, and recent thoracic surgery (within the preceding 3 weeks) or pneumothorax. Decreased outdoor activity at the destination should be considered if air pollution is excessive. . Chapter 117. Health Advice for International Travel (Part 7) Gastrointestinal Illness Decreased levels of gastric acid,. P450. Chronic Illness, Disability, and Travel Chronic health problems need not prevent travel, but special measures can make the journey safer and more comfortable. Heart Disease Cardiovascular. supplementary oxygen should be ordered by the traveler's physician well before flight time. Travelers may benefit from aisle seating and should walk, perform stretching and flexing exercises,