Cocirculation of genotypes D4 and D6 in Greece during the 2005 to 2006 measles epidemic.

One of World Health Organization's proposed methods for the establishment of measles surveillance worldwide, to achieve the elimination of measles virus by 2010, is the genetic characterization of measles wild-type virus strains. In this study, 34 measles virus strains, isolated from clinical samples during the 2005 to 2006 measles outbreak in Greece, were genotyped and studied in terms of nucleotide variation and phylogeny. Interestingly, the cocirculation of 2 different genotypes, namely, D6 and D4, was revealed. In fact, the D4 genotype has never been previously reported in Greece. Finally, although the D4 Greek strains possessed identical nucleotide sequences, the D6 isolates segregated into 3 distinct subgroups, 2 of which differed genetically and phenotypically from all GenBank deposited measles sequences. It is, thus, important to continue the epidemiologic surveillance of measles in Greece to aid future studies of measles transmission, monitor the effectiveness of measles immunization, and eventually document the elimination of the virus in our country.