Abstract
A Danish school class travelled under primitive circumstances in East Africa for 28 d. Four out of 18 persons had febrile illnesses interpreted as malaria during the journey. Retrospective serological testing for antibodies against the P. falciparum circumsporozoite protein indicated a transmission rate of more than 80% despite extensive protection against mosquito bites. The study demonstrates the use of serological evaluation of malaria transmission risk as well as retrospective immunodiagnosis of clinical malaria. Three of the travellers with febrile illnesses used self-medication with mefloquine, and in 2 of the cases a diagnosis of malaria was supported by a positive immunofluorescence assay for malaria antibodies.