Abstract A Bwamba group virus was isolated from the blood of a febrile child on the Kano Plain, Kenya. The isolate (NY‐45), closely resembling Bwamba, established infection in both Anopheles gambiae and Mansonia uniformis. Neither the Bwamba nor the Pongola prototype strains grew in both species. In gel‐diffusion tests NY‐45 virus passaged through mosquitoes exhibited a line of identity with Pongola antiserum. In contrast no cross‐reaction was observed with NY–45 virus which had not previously been passaged through mosquitoes.