Etiology of influenza-like illnesses in the population of Novosibirsk city in the 2018–2019 epidemic season

Abstract

Influenza and other acute respiratory viral infections lead to a substantial incidence of severe cases and hospitalizations and so remain a global health problem. Within the frame of the Global Influenza Hospital Surveillance Network (GIHSN), we assessed the contribution of influenza and other respiratory viruses to severe cases of influenzalike diseases in patients hospitalized to the Novosibirsk infectious hospitals in the years 2018–2019. We analyzed 484 nasopharyngeal swabs collected from patients admitted to the hospitals with acute respiratory infections (ARI) using real-time polymerase chain reaction commercial kits. We confirmed viral etiology of ARI in 69.8% cases. Influenza viruses were detected in 47.1% cases, wherein concomitant circulation of influenza A(H1N1)pdm09 and A(H3N2) viruses was observed in 20.7% and 26% of patients, respectively, whereas influenza B virus was detected only in one sample. All analyzed influenza A viruses were antigenically similar to vaccine strains. Genetically, the Novosibirsk strains were closely related to influenza A viruses distributed in Russia and worldwide. Influenza A(H1N1)pdm09 virus was detected in all patients aged 0 to 14 years and required intensive care. Other respiratory viruses were detected in 36.4% of children and 5.8% of adults, and 8.3% of children had viral coinfection, whereas no cases of coinfection were detected in adults. The most common viruses in children were metapneumovirus — 12.8%, rhinovirus — 9.3% and respiratory syncytial virus — 8.0%. In adults, metapneumovirus, adenovirus, parainfluenza virus and rhinovirus were detected with a detection rate no exceeding 2%. In this study, we found no differences in the detection rate of the influenza virus due to concomitant chronic diseases, pregnancy, or smoking habits. At the same time, the detection rate of other respiratory viruses in non-smokers vs. smokers was significantly lower than in smokers and former smokers (26.15%, 66.67% and 62.50%, respectively). In addition, the level of detection of respiratory viruses in children with vs. without chronic pathology was significantly higher (55.3% and 38.7%, respectively). Thus, our and similar studies are important for monitoring and control of the infection.