A multinational outbreak of histoplasmosis following a biology field trip in the Ugandan rainforest

Outbreaks of histoplasmosis have been increasingly reported in association with travel to endemic areas. Multiple outbreaks have been reported following travel to the Americas, but reports of pulmonary histoplasmosis in short-term immunocompetent travelers to Africa are rare.

A biology student was referred to our unit with suspected pulmonary histoplasmosis following her return from a field trip in the Ugandan rainforest. The patient informed us that several of her multinational student colleagues on the same expedition had developed a similar illness. Using an alert in ProMED-mail and a questionnaire forwarded to each of the symptomatic students, we accumulated data on the other cases involved in this apparent outbreak of pulmonary histoplasmosis.

Thirteen of 24 students developed respiratory symptoms following the expedition. Chest X-ray appearances were often suggestive of miliary tuberculosis but in most cases a final diagnosis of histoplasmosis was made (confirmed with serology in five cases, clinically diagnosed in six, and retrospectively suspected in two). Detailed questioning indicated that the likely source was a large hollow bat-infested tree within the rainforest.

This is an unusual outbreak of histoplasmosis following short-term travel to Africa. Pulmonary histoplasmosis should always be considered in the differential diagnosis of an acute febrile respiratory illness in travelers returning from endemic areas or reporting activities suggesting exposure.