Associations between Burkitt Lymphoma among children in Malawi and infection with HIV, EBV and malaria: results from a case-control study by Mutalima, N, Molyneux, E, Jaffe, H, Kamiza, S, Borgstein, E, Mkandawire, N, Liomba, G, Batumba, M, Lagos, D, Gratrix, F, Boshoff, C, Casabonne, D, Carpenter, L, Newton, R