engleski

Variability and evolution of pneumoviruses in Croatia, 2011-2016

Acute respiratory tract infection (ARTI) is the most common infection in children under 5 years of age and it is frequently induced by two pneumoviruses ; human respiratory syncytial virus (HRSV) and human metapneumovirus (HMPV). Epidemic seasons of these viruses overlap and disease manifestations are highly similar, including severe lower ARTI such as bronchiolitis or pneumonia. Due to the variability among strains reinfections with pneumoviruses are frequent, with yearly outbreaks of both viruses. The molecular epidemiology of pneumoviruses is rather complex as numerous genotypes exist, new genotypes emerge and some previously circulating genotypes appear to become extinct. Hence, limited prevention treatment is available. Genetic diversity of HRSV and HMPV strains circulating in Croatia was monitored during six consecutive years, March 2011-March 2016. Samples were obtained from patients with DFA-confirmed HRSV or HMPV infection ; further molecular analyses were based on sequences of the second hypervariable region of the HRSV G gene or partial HMPV F gene. In HRSV group A, NA1 was predominant genotype during first 3 years of the study, followed by rapid replacement with newly introduced genotype ON1. At the beginning of 2016, 70% of analyzed HRSV samples were of ON1 genotype showing clear genotype shift in the circulating HRSV population. Within HMPV strains, the presence of a novel group A subcluster (A2c) was detected ; A2c subcluster was present during the entire study period, except in 2013. In HMPV group A 40% of the strains classified as A2c. Prior to our analysis, this subcluster has only been detected in Japan (2010- 2011) and Malaysia (2012-2014). Throughout the study period a higher substitution rate (9.94 × 10−3/site/year) was observed within HRSV group B strains compared to the group A strains (4.98 × 10−3/site/year for ON1 strains). Both HMPV group A and group B strains had similar substitution rates of approx. 2.4×10−3/site/year and showed the same degree of genetic diversity.

human respiratory syncytial virus ; human metapneumovirus ; variability ; molecular evolution

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