Sera of 486 schoolchildren from four communal areas in Zimbabwe were tested by the indirect fluorescent antibody techhnique for antibodies to Crimean Congo haemorrhagic fever, Rift Valley fever, Lassa, Ebola and Marburg virus; Crimean Congo haemorrhagic fever and Ebola-Zaire virus were shown to have been active in all four areas and Marburg virus in three of the four areas tested.