Molecular Characterization of Avian-like H1N1 Swine Influenza A Viruses Isolated in Eastern China, 2011

Currently, three predominant subtypes of influenza virus are prevalent in pig populations worldwide: H1N1, H3N2, and H1N2. European avian-like H1N1 viruses, which were initially detected in European pig populations in 1979, have been circulating in pigs in eastern China since 2007. In this study, six influenza A viruses were isolated from 60 swine lung samples collected from January to April 2011 in eastern China. Based on whole genome sequencing, molecular characteristics of two isolates were determined. Phylogenetic analysis showed the eight genes of the two isolates were closely related to those of the avian-like H1N1 viruses circulating in pig populations, especially similar to those found in China. Four potential glycosylation sites were observed at positions 13, 26, 198, 277 in the HA1 proteins of the two isolates. Due to the presence of a stop codon at codon 12, the isolates contained truncated PB1-F2 proteins. In this study, the isolates contained 591Q, 627E and 701N in the polymerase subunit PB2, which had been shown to be determinants of virulence and host adaptation. The isolates also had a D rather than E at position 92 of the NS1, a marker of mammalian adaptation. Both isolates contained the GPKV motif at the PDZ ligand domain of the 3' end of the NS1, a characteristic marker of the European avian-like swine viruses since about 1999, which is distinct from those of avian, human and classical swine viruses. The M2 proteins of the isolates have the mutation (S31N), a characteristic marker of the European avian-like swine viruses since about 1987, which may confer resistance to amantadine and rimantadine antivirals. Our findings further emphasize the importance of surveillance on the genetic diversity of influenza A viruses in pigs, and raise more concerns about the occurrence of cross-species transmission events.

Etiological characteristics of influenza-like illness in Jiangsu province from 2012 to 2016

Influenza-like illness(ILI)is an acute respiratory infection caused by various pathogens.However,the epidemiologic characteristics of ILI pathogens in Jiangsu province are unclear.To better understand the ILI etiology,the characteristics of the pathogens from nasopharyngeal swab samples of patients with ILI collected from 2012 to 2016 in 6 hospitals in Jiangsu province were studied.The pathogens,including influenza virus,respiratory syncytial virus(RSV),rhinovirus(HRV),adenovirus(ADV),herpes simplex virus(HSV),human coronavirus(hCoV),Streptococcus pneumoniae and Haemophilus influenzae,were detected by real-time PCR.At least one pathogen was identified in 1334 of the patients(40.23%).Among viruses,HRV,influenza A virus(Flu A),ADV and RSV were the most frequently detected.ADV was the only pathogen that was distributed evenly in different years and regions(P>0.05).The etiological distribution varied in different age groups.Streptococcus pneumoniae was the most common pathogen in co-infections with a co-detection rate of 64.57%(319/494).The spectrum of etiologies could help to estimate disease burden and provide guidance for vaccination.