Objective To analyze the prevalence status and the genetic characterizations of influenza B viruses isolated in Hunan Province after pandemic influenza A (H1N1) 2009,and to explore possible reasons for the prevalence.MethodsThroat swabs were collected from outpatients with influenza-like illness in 23 sentinel hospitals of Hunan Province in 2010.Influenza viruses were isolated with Madin-Darby canine kidney (MDCK) cells and identified by haemagglutination inhibition test.The genomes of 10 selected influenza B viruses were sequenced and analyzed for phylogenetic and molecular characterization.ResultsWith the reduction of isolation of pandemic influenza A (H1N1)2009 viruses,influenza B virus became the predominant isolated strain in the first half of 2010.Epidemic viruses mainly belonged to the B/Victoria lineage,and both two lineages co-circulated.Seven out of 11 influenza outbreaks caused by type B.Ten strains were filled into 2 branches of BV and BY which were classified by their lineage types in polymerase (PB2,PB1,PA),hemagglutinin (HA),neuraminidase (NA),NB,membrane protein (M1),influenza B virus membrane protein M2 (BM2),and non-structural protein (NS1,NS2) phylogenetic trees except the NP phylogenetic tree in which 10 strains were all in the BY branch.Compared with World Health Organization (WHO) vaccine strains,the amino acid identity of 11 proteins of the 10 strains was high (97.2％-100.0％).However,some amino acid point mutations were found.No mutation was found in drug resistance mutation sites.Some mutations in NA,NB,PB1,PB2 and NS2 molecules were found in 2 strains isolated from outbreaks compared with strains from sentinel surveillance.Conclusions The point mutations,insertions and genetic reassortment indicate viruses sustaining evolution,which is probably the reason for predominant influenza B viruses after pandemic influenza A (H1N1) 2009 in Hunan Province.

Objective: To analyze the genome characteristics of an avian influenza A (H9N2) virus isolated from an 11-month-old infant, and to look for possible sources of infection. Methods: Throat swabs were collected from an infant with influenza-like illness in influenza sentinel surveillance hospitals and isolated for influenza viruses using cells. The isolates were identified for influenza virus types and subtypes by the method of hemagglutination assay, hemagglutination inhibition assay and fluorescence PCR. Whole genome sequencing of the isolated virus was carried out. The genome nucleic acid sequences and the deduced amino acid sequences were analyzed by comparing the phylogenetic trees which were constructed by bioinformatics software. Results: A seasonal un-typed influenza virus was isolated from the infant with influenza like illness. With fluorescent PCR method , it was identified as H9N2 subtype of avian influenza virus and the case was confirmed as a human infected with an avian influenza A(H9N2) virus. Epidemiological studies revealed that the case had no clear history of poultry contact and exposure. Blast analysis shows that eight segments of the viral genome are avian origin, and 97.5%-99.8% homology with that of viruses isolated from the live-poultry markets. The virus belongs to G57 genotype, deduced amino acid sequence analysis shows that the virus has typical low pathogenic avian influenza characteristics. Conclusions Although the case does not have a clear history of contact or exposure to poultry, molecular traceability suggests that possible sources of infection may be still from poultry.

OBJECTIVETo identity the clinical characteristics and severe case risk factors for the adult inpatient cases confirmed of influenza monitored by the sentinel surveillance system for severe acute respiratory infection (SARI) inpatient cases in ten provinces in China.

METHODSEpidemiology and clinical information surveys were conducted for adult cases (≥ 15 year old) consistent with SARI case definition, who were monitored by SARI sentinel hospitals in ten cities in China from December 2009 to June 2014, with their respiratory tract specimens collected for influenza RNA detection. Adult SARI cases were classified into influenza inpatient group and outpatient group by the detection outcomes, analyzing their demographic information, clinical and epidemiology characteristics respectively, in addition to risk factors for severe inpatient cases.

RESULTS3 071 adult SARI cases were recruited from ten hospitals, including 240 (7.8%) cases of laboratory-confirmed influenza, most of them being A (H1N1) pdm2009 and A (H3N2) sub-types. Age M of the included influenza cases was 63 year old, 47.1% of them being ≥ 65 seniors. 144 (60.0%) cases of the influenza inpatients suffered from at least one chronic underlying condition, and the proportion of emphysema (7.9%) was higher than non-influenza inpatient cases (3.8%), being statistically significant (χ(2) = 3.963, P = 0.047). 19.4% of the women of childbearing age infected of influenza were in pregnancy, and only 1.1% of the 240 influenza cases had been vaccinated against influenza. The proportion of sore throat and dyspnea found among influenza inpatients was higher than inpatients without influenza. 17.4% of the influenza cases were accepted into ICU for treatment, with no statistical significance with non-influenza inpatient cases (P = 0.160). 23.1% of the influenza inpatients received an antiviral drug therapy, a figure higher than the non-influenza inpatient cases (4.8%) (P < 0.001). 41.5% of the inpatients developed complications, with the proportion of viral pneumonia significantly higher than the non-influenza inpatient cases (P < 0.001). Asthma (RR = 15.200, 95% CI: 1.157-199.633), immunosuppressive diseases (RR = 5.250, 95% CI: 1.255-21.960), pregnancy (RR = 21.000, 95% CI: 1.734-254.275), time interval from onset to admission less 7 days (RR = 1.673, 95% CI: 1.071-2.614) were identified as risk factors of severely-ill influenza cases.

CONCLUSIONIt was found that adult influenza inpatients were mostly ≥ 65 year old seniors. The influenza vaccination rate among the influenza cases was very low, and antivirus drugs were used less than necessary. In this regard, influenza vaccination was recommended for high risk groups of pregnant women, seniors and chronic disease patients on annual basis, while influenza inpatients were advised to use antiviral drugs as early as possible.

Adult ; Aged ; Antiviral Agents ; China ; epidemiology ; Female ; Hospitalization ; Humans ; Influenza A Virus, H1N1 Subtype ; Influenza A Virus, H3N2 Subtype ; Influenza, Human ; epidemiology ; Inpatients ; Outpatients ; Pneumonia, Viral ; Pregnancy ; Respiratory Tract Infections ; Risk Factors ; Sentinel Surveillance ; Vaccination