Isolations of Bwamba virus from south central Uganda and north eastern Tanzania.

Julius J. Lutwama, Elly B. Rwaguma, Peter L. Nawanga and Anthony Mukuye
Department of Arbovirology, and Emerging and
Re-emerging Viral Infections
Uganda Virus Research Institute,
P.O. Box 49, Entebbe, Uganda.

ABSTRACT
Background:
Bwamba virus (Genus Bunyavirus, family Bunyaviridae) is widely distributed in Africa. It causes many unidentified fevers because of its benign nature.

Objectives:
Samples of blood from patients were received at Uganda Virus Research Institute for diagnosis and confirmation of infections. Mosquito collections obtained in the O’nyong-nyong virus fever epidemic in Rakai in 1997 were also investigated in an effort to confirm the vectors of O’nyong-nyong virus fever.

Methods:
Patients’ serum and aliquots of mosquito pools were inoculated into the brain of 1-day old albino mice for attempted isolation of viruses. Positive isolates from sick mice were confirmed to be Bwamba virus by immunoflourescence assay microscopy and by plaque reduction neutralization tests.

Results:
Three positive isolates of Bwamba virus were obtained. One of the strains was isolated from a sample of blood from a refugee in Burigi Camp, Ngara, in north eastern Tanzania; another strain was isolated from a health worker at the Uganda Virus Research Institute, working with the Rakai Project on HIV in Rakai district; while the third strain was isolated from a pool of 50 Anopheles funestusmosquitoes collected during the O’nyong-nyong virus fever epidemic in Rakai district in 1996/1997.

Conclusions:
Bwamba fever may be more common than it is usually thought to be. It is often mistaken for malaria and because it is a mild infection, many people do not go to hospital when infected. Further studies are needed to understand the epidemiology and natural history of Bwamba virus.