Travellers with pre-existing medical conditions.

Medical conditions that influence travel include those that compromise the immunity of the traveller and chronic underlying diseases or infirmities. The former includes HIV, transplantation, malignancy and its treatment, IgA deficiency, asplenia and use of immunocompromising drugs like corticosteroids. Chronic conditions include diabetes mellitus, end stage renal disease, diseases associated with compromised cardiac or pulmonary function and certain gastrointestinal diseases including cirrhosis. This review includes practical approaches to each of these conditions with attention to risk assessment and avoidance, vaccination when appropriate and not a risk to the compromised host, and arming the traveller with self-therapy and chemoprophylaxis. Since travellers with underlying conditions are often taking various medications the travel health practitioner must be alert for possible drug/drug interactions and must adjust dosages depending on the level of compromised renal or hepatic function. Finally, education of such travellers is paramount; they must understand that risk avoidance is critical and preventative modalities such as vaccination and chemoprophylaxis are never 100% efficacious.