Monitoring of measles elimination using molecular epidemiology.

The different measles virus genotypes are confined to more or less distinct geographic regions. Molecular characterization of virus isolates has been successfully used to determine epidemiological links between cases and the geographic origin of imported viruses. In Europe, indigenous measles has been eliminated in some countries, but in others the disease is still endemic. Intra-outbreak variability can be used to differentiate between sporadic endemic cases and a 'pseudo-outbreak' of unrelated imported cases. The interruption of virus circulation by mass vaccination campaigns could be demonstrated by comparing the variability of pre-campaign viruses with post-campaign isolates. Simplified tools are being developed that could bring genotyping within reach of laboratories that do not have the possibility of sequencing.