Background: A recent longitudinal study in the Dadaab refugee camp near the Kenya-Somalia border identified\nunusual biannual respiratory syncytial virus (RSV) epidemics. We characterized the genetic variability of the associated\nRSV strains to determine if viral diversity contributed to this unusual epidemic pattern.\nMethods: For 336 RSV positive specimens identified from 2007 through 2011 through facility-based surveillance\nof respiratory illnesses in the camp, 324 (96.4%) were sub-typed by PCR methods, into 201 (62.0%) group A, 118\n(36.4%) group B and 5 (1.5%) group A-B co-infections. Partial sequencing of the G gene (coding for the attachment\nprotein) was completed for 290 (89.5%) specimens. These specimens were phylogenetically analyzed together with\n1154 contemporaneous strains from 22 countries.\nResults: Of the 6 epidemic peaks recorded in the camp over the period, the first and last were predominantly made\nup of group B strains, while the 4 in between were largely composed of group A strains in a consecutive series of\nminor followed by major epidemics. The Dadaab group A strains belonged to either genotype GA2 (180, 98.9%) or\nGA5 (2, < 1%) while all group B strains (108, 100%) belonged to BA genotype. In sequential epidemics, strains within\nthese genotypes appeared to be of two types: those continuing from the preceding epidemics and those newly\nintroduced. Genotype diversity was similar in minor and major epidemics.\nConclusion: RSV strain diversity in Dadaab was similar to contemporaneous diversity worldwide, suggested both\nbetween-epidemic persistence and new introductions, and was unrelated to the unusual epidemic pattern.
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