Measles virus nomenclature update: 2012.

The genetic characterization of circulating wild-type viruses is a critical component of measles laboratory surveillance and molecular epidemiological studies. The combination of molecular analysis and standard case investigation provides a sensitive means to describe the transmission pathways of measles virus and to document the interruption of endemic measles transmission. Absence of endemic genotype(s) is one of the criteria for verifying measles elimination in a country or region.1 A standardized methodology and nomenclature is used to define measles sequences and genotypes. Two global reporting platforms have been developed to collect and analyse sequence data, the WHO Global Measles and the Measles Nucleotide Surveillance (MeaNS) databases. The nomenclature used to describe the genetic diversity of wild-type measles viruses was proposed initially by WHO in 1998,2 and was reviewed and updated in 2001, 2003, 2005 and 2006.3 This report updates the existing documentation and incorporates the significant increase of data generated by the WHO laboratory network (LabNet)4 in the last decade. In addition, this report clarifies the standard naming convention for measles virus, and introduces 2 databases that enable reporting, storage, and analysis of genotype information. Functional considerations relating to the mechanism of genotype classification and intra-genotype variation/ stratification are also discussed.