Affiliation: | National Institute of Communicable Diseases, Johannesburg, South Africa (K.H. Keddy, A.M. Smith, A. Sooka, H. Ismail);University of the Witwatersrand, Johannesburg (K.H. Keddy, A.M. Smith, H. Ismail);National Health Laboratory Service, Groote Schuur, Cape Town, South Africa (S. Oliver);University of Cape Town, Cape Town (S. Oliver) |