Rubella epidemiology in the Central African Republic, 2015-2016 and molecular characterization of virus strains from 2008-2016

Abstract

Purpose: The Central African Republic (CAF) has not yet introduced immunization against rubella in its national immunization program. In addition, neither rubella nor congenital rubella syndrome (CRS) are integrated into the epidemiological surveillance system. Rubella virus belongs to the genus Rubivirus in the family Matonaviridae. It is an RNA virus with a single serotype, but 13 genotypes grouped in two clades. With an estimated 100.000 cases worldwide each year, CRS is a major public health problem. The aim of this retrospective study was to investigate rubella epidemiology between 2015 and 2016 and to provide baseline genotype data for monitoring the coming rubella control efforts. Methods & Materials: Sera collected from measles suspected cases between 2015 and 2016 and tested negative or equivocal for measles-specific IgM antibodies were investigated for rubella-specific IgM antibodies using commercially available ELISA kits. To obtain baseline data of the circulating rubella virus genotypes, 350 rubella IgM positive specimens taken within 3 days of rash onset between 2008 and 2016 were submitted to RT-PCR, sequencing of the partial E1 gene and phylogenetic analyses. Results: 831 measles IgM negative or equivocal sera from 2015/2016 were tested for rubella IgM antibodies and 411 (49.5%) of them were rubella IgM positive. Most of the IgM positive cases (n=391, 95.1%) were collected between January and April. Most patients were between 5 and 9 years old (50.2%) and only 18 patients were older than 15 years (4.4%), but 15 of them were females. Sequencing was possible for 37 of the 350 selected rubella IgM-positive specimens. Phylogenetic analysis identified three different genotypes of rubella virus, namely 1E (n=12), 1G (n=5) and 2B (n=20). Conclusion: Our study confirmed the importance of rubella as cause of rash and fever in CAF and the importance of implementing rubella and CRS surveillance in the country. Our analyses provide comprehensive data on rubella epidemiology and highlight that genotype data may be obtained using samples collected for antibody detection even in very challenging settings.