Measles virus genotype B2 is not inactive: evidence of continued circulation in Africa

This study describes two measles outbreaks--one in Cape Town, South Africa in November 2002, and the other in Luanda, Angola in March 2003. The outbreaks were notable because they were caused by closely related genotype B2 viruses. This genotype was first described in an outbreak in Libreville, Gabon in the 1980s and was labeled as inactive by the World Health Organization in 2003 because it had not been detected for over 15 years. As the first three cases in the Cape Town outbreak were Angolan citizens who recently arrived from Angola, it appears likely that the source of the virus was Angola. Molecular analysis of specimens collected during the outbreak in Luanda provided direct evidence for the circulation of genotype B2 measles virus (MV) in Angola. This study clearly demonstrates that there is still active circulation of genotype B2 in Africa, and we propose that its apparent inactivity is merely the result of insufficient virologic/molecular surveillance in the region. These findings highlight the need for expanded molecular surveillance in Africa.