Molecular genetic characteristics of influenza A virus clinically isolated during 2011‐2016 influenza seasons in Korea

Abstract

BackgroundThe influenza virus is reportedly associated with 3‐5 million cases of severe illness and 250 000‐500 000 deaths annually worldwide.ObjectivesWe investigated the variation of influenza A virus in Korea and examined the association with death.MethodsA total of 13 620 cases were enrolled in the Hospital‐based Influenza Morbidity & Mortality surveillance system in Korea during 2011‐2016. Among these cases, a total of 4725 were diagnosed with influenza using RT‐PCR (influenza A; n = 3696, influenza B; n = 928, co‐infection; n = 101). We used 254 viral sequences from the 3696 influenza A cases for phylogenetic analysis using the BioEdit and MEGA 6.06 programs.ResultsWe found that the sequences of A/H3N2 in the 2011‐2012 season belong to subgroup 3C.1, whereas the sequences in the 2012‐2013 season pertain to subgroup 3C.2. The sequences in the 2013‐2014 and 2014‐2015 seasons involve subgroups 3C.3a and 3C.2a. The A/H1N1pdm09 subtype belongs to subgroup 6 and contains two clusters. In addition, sequence analysis confirmed the several substitutions of internal genes and gene substitutions associated with drug resistance (I222V in NA and S31N in M2) in the fatal cases. While statistical analysis found no significant associations between genetic differences in the viruses and mortality, mortality was associated with certain host factors, such as chronic lung disease.ConclusionsIn conclusion, influenza A virus clade changes occurred in Korea during the 2011‐2016 seasons. These data, along with antigenic analysis, can aid in selecting effective vaccine strains. We confirmed that fatality in influenza A cases was related to underlying patient diseases, such as chronic lung disease, and further studies are needed to confirm associations between mortality and viral genetic substitutions.

Molecular epidemiology survey and characterization of human influenza A viruses circulating among Palestinians in East Jerusalem and the West Bank in 2015

“…This result was in accordance with the WHO, regional and international reports of the same season [9, 24, 28, 35, 43–45]. Interestingly, the neuraminidase gene sequences of all Palestinian A(H3N2) were closely related to A/Switzerland/9715293/2013(H3N2), subclade 3C.3a, which was a distinctive finding observed for the A(H3N2) isolates from 2015 [35, 45]. Each of non-synonymous substitutions N144S, N144R and N122D remove a potential N-glycosylation site, while K160T and N128T create a new potential N-glycosylation, with the consequences of affecting antigenic properties [12].…”

“…Ten Palestinian 2015 A(H3N2) isolates fell into subclade 3C.2a, one into clade 3C.2, and one into clade 3C.3, respectively. This result was in accordance with the WHO, regional and international reports of the same season [9, 24, 28, 35, 43–45]. Interestingly, the neuraminidase gene sequences of all Palestinian A(H3N2) were closely related to A/Switzerland/9715293/2013(H3N2), subclade 3C.3a, which was a distinctive finding observed for the A(H3N2) isolates from 2015 [35, 45].…”

“…The Palestinian A(H1N1)pdm09 isolates fell into clade 6B. A(H1N1)pdm09 with clade 6B were predominant for season 2014/2015 as indicated by the WHO [9], regional [24], and International reports [33–35]. Most of the 6B clade-defining substitutions evolved during the last years and were reported earlier in some studies before being attributed to the new clades.…”

Potent anti-influenza H7 human monoclonal antibody induces separation of hemagglutinin receptor-binding head domains

“…Influenza evolution, particularly in HA, occurs rapidly, with antigenic drift sometimes conferred by single amino acid changes near the RBS [2]. The RBS, which is the most conserved region of the HA head, forms a shallow pocket to which a series of antibodies has been shown to bind and neutralize [3].…”

The National Influenza Surveillance System of Korea

“…Influenza-related statistics and collected data are reported on a daily and weekly basis. The HIMM data have been used to analyze the clinical course of severe influenza [2627], influenza disease burden [28], characteristics of influenza viruses that caused severe clinical course [29], influenza vaccine effectiveness, and so on. In addition to surveillance for severe influenza, there is surveillance for avian influenza viruses that can cause human infection such as A/H7N9 and A/H5N1 [30].…”