ABSTRACT
Objective To analyze the surveillance results of influenza-like illness ( ILI) and investigate the prevalent trend of influenza from 14th week 2017 to 13th week 2018 (April 3, 2017-April 1, 2018) in Qinghai Province so as to provide the scientific basis for the development of prevention and control measures. Methods The epidemiological and pathogenic characteristics of influenza-like cases in qinghai province from 14th week 2017 to 13th week 2018 were collected and analyzed. Results ILI mainly occurred in winter and spring from 14th week 2017 to 13th week 2018,26 086 ILI cases reported in total，accounting for 2.95% (26 086/884 529) of total number of outpatients and emergency cases; including 18 655 cases under 5 years old，accounting for 71.51%; 1 991 cases were detected with positive by real -time RT PCR with the positive rate of 17.48% (1 991/11 391), In the early stage, H3 and H1 were the predominate strains and the middle period was mixed with H3, H1 and B, and the latter was dominated by type B. Positive rates of influenza virus testing had no statistical differences in different gender ( 2=5.33, P=0.021)，while with statistical differences in different age and time ( 2=108.59, P<0.001; 2= 1 629.13, P<0.001). Number of ILI cases and the percentage in the outpatients was significantly related with influenza virus positive rates (Pearson correlation coefficient was 0.896 and 0.699, respectively, P<0.001). Conclusions Influenza-like cases at sentinel hospital of Qinghai Province can accurately reflect actual activity level. The peak of positive detection of influenza samples in Qinghai province from 14 weeks 2017 to 13 weeks 2018 season was from mid-December to mid-January. The dominant strain of influenza viruses alternated, and the majority of the affected population is mainly in children under 5 years old. In the future, we should strengthen monitoring works in epidemic season, from October to March of next year and focus on the children under 5 years old and the fever clinic. The collection of samples of influenza-like cases in the 0-year-old group should be strengthened, and collective organizations should focus on influenza prevention and control.
ABSTRACT
This study aims to perform a survey of genetic variation in neuraminidase (NA) gene of influenza A/H3N2 virus, as well as related resistance to NA inhibitors, in Qinghai Province of China, 2010 to 2012. Strains of influenza A/H3N2 isolated during an influenza survey from 2010 to 2012 in Qinghai were enrolled by random sampling. Viral RNA was extracted and amplified by RT-PCR. Purified PCR products were sequenced thereafter. Genetic analysis of nucleic acid and the derived amino acid sequences was performed by MEGA 4.0. Phylogenetic trees were also constructed. Strains isolated during 2010-2011 in this study clustered closely with World Health Organization (WHO) 2010-2012 reference vaccine strain A/Perth/16/2009 and 2008-2010 reference vaccine strain A/Brisbane/10/2007 on the phylogenetic tree, while the 2012 isolates were located on another branch. In analysis of derived amino acid sequences, the 2010 isolates mutated at K81T, the 2011 isolates mutated at I26V and D127N, while the 2012 isolates mutated at E41K, P46A, I58V, T71N, L81P, D93G, D127N, D151N, and I307M. The D151N mutation added a glycosylation site to the activity center of NA. No significant variation was discovered in H3N2 NA gene of 2010-2011 isolates in Qinghai, China. Isolates of 2012 were found with significant mutation, which has the potential of inducing minor resistance to NA inhibitors like zanamivir and oseltamivir.