1 Bunyamwera virus was isolated from a batch of 290 Aedes (Banksinella) circumluteolus mosquitoes caught near Lake Simbu in the Ubombo district of northern Natal in April, 1955.
2. Rift Valley fever virus was isolated from another batch of 195 Aedes (Banksinella) circumluteolus mosquitoes caught in the same region in May, 1955.
3. A further batch of 300 Aedes circumluteolus mosquitoes caught on 28th April and processed as one pool, gave rise to the isolation of virus which appears to have been a mixture of Bunvamwera and Rift Valley fever viruses.