aGlobal Heath and Tropical Medicine and Unidade de Saúde Pública Internacional e Bioestatística, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Lisbon, PortugalbUniversity Hospitals Leuven, AIDS Reference Laboratory, HerestraatcKU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Clinical and Epidemiological Virology, Minderbroederstraat, Leuven, Belgium.