1. Field Epidemiology and Laboratory Training Programme, Ministry of Health and Social Welfare, Dar es Salaam, Tanzania.
2. Department of Microbiology and Immunology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania.
3. Department of Clinical Science and Education, Sodersjukhuset and Karolinska Institutet, Stockholm, Sweden.
4. Institute of Infectious Disease and Molecular Medicine, Division of Medical Virology, University of Cape Town, Cape Town, South Africa.