Genetic characterization and diversity of circulating influenza A/H1N1pdm09 viruses isolated in Jeddah, Saudi Arabia between 2014and 2015

AbstractThe emerged influenza A/H1N1pdm09 viruses have replaced the previously circulating seasonal H1N1 viruses. The closeantigenic properties of these viruses to the 1918 H1N1 pandemic viruses and their post-pandemic evolution pattern couldfurther enhance their adaptation and pathogenicity in humans representing a major public health threat. Given that data onthe dynamics and evolution of these viruses in Saudi Arabia is sparse we investigated the genetic diversity of circulatinginfluenza A/H1N1pdm09 viruses from Jeddah, Saudi Arabia, by analyzing 39 full genomes from isolates obtained between2014-2015, from patients with varying symptoms. Phylogenetic analysis of all gene segments and concatenated genomesshowed similar topologies and co-circulation of clades 6b, 6b.1 and 6b.2, with clade 6b.1 being the most predominate since2015. Most viruses were more closely related to the vaccine strain (Michigan/45/2015) recommended for the 2017/2018season, than to the California/07/2009 strain. Low sequence variability was observed in the haemagglutinin protein comparedto the neuraminidase protein. Resistance to neuraminidase inhibitors was limited as only one isolate had the H275Y substitution.Interestingly, two isolates had short PA-X proteins of 206 amino acids compared to the 232 amino acid protein foundin most influenza A/H1N1pdm09 viruses. Together, the co-circulation of several clades and the predominance of clade 6b.1,despite its low circulation in Asia in 2015, suggests multiple introductions most probably during the mass gathering eventsof Hajj and Umrah. Jeddah represents the main port of entry to the holy cities of Makkah and Al-Madinah, emphasizing theneed for vigilant surveillance in the kingdom