IMPLEMENTATION OF A NATIONAL MEASLES ELIMINATION PROGRAM IN IRAN: PHYLOGENETIC ANALYSIS OF MEASLES VIRUS STRAINS ISOLATED DURING 2010–2012 OUTBREAKS

Monday, 18th of August 2014 Print
[source]PLoS One[|source]

Small and large outbreaks have occurred periodically in Iran. Two different measles genotypes have been reported from 2002-May 2010 in Iran. Genotype D4 was considered as the indigenous genotype before mass vaccination and genotype H1 as imported genotype from distant parts of Asia.

In this report, the authors obtain insights into the molecular epidemiology of recent measles outbreaks in all provinces of Iran and compare virus strains to strains found in epidemics in other parts of the world. The report documents that in Iran a) significant reductions in genotype D4 circulation has occurred, b) the dominat genotpe is now B3 and H1 and c) that transmission of measles virus was not interrupted until 2012. More details and recommendations are accessible at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3988093/

 

ABSTRACT

Measles virus (MV) causes small and large outbreaks in Iran. Molecular assays allow identifying and the sources of measles imported from neighboring countries. We carried out a phylogenetic analysis of measles virus circulating in Iran over the period 2010–2012. Specimens from suspected cases of measles were collected from different regions of Iran. Virus isolation was performed on urine and throat swabs. Partial nucleoprotein gene segments of MV were amplified by RT-PCR. PCR products of 173 samples were sequenced and analyzed. The median age of confirmed cases was 2 years. Among all confirmed cases, 32% had unknown vaccination status, 20% had been vaccinated, and 48% had not been vaccinated. Genotypes B3 and D8 (for the first time), H1 and D4 were detected mainly in unvaccinated toddlers and young children. Genotype B3 became predominant in 2012 and was closely related to African strains. H1 strains were also found in small and large outbreaks during 2012 but were not identical to Iranian H1-2009 strains. A majority of the Iranian D4 strains during 2010–2012 outbreaks were linked to the D4 strain identified in the Pakistan in 2007. We identified a single case in 2010 belonging to D8 genotype with 99.7% identity to Indian isolates. Although the vaccination program is currently good enough to prevent nationwide epidemics and successfully decreased measles incidence in Iran, the fraction of protected individuals in the population was not high enough to prevent continuous introduction of cases from abroad. Due to increasing number of susceptible individuals in some areas, sustained transmission of the newly introduced viral genotype remains possible.

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