Epidemiological survey of H3 influenza outbreak in a shoe factory in Shenzhen

Objective　The study was conducted to investigate the cause and characteristics of a influenza outbreak in a large-scale shoe factory in Shenzhen, and analyze the laboratory findings, provide the evidence for the surveillance and management of influenza outbreak. Methods　Epidemiological survey was conducted for the influenza-like cases, and the throat swabs were taken from the patients for colloidal gold screening tests and quantitative fluorescent RT-PCR detection, and the isolation and identification of influenza virus. Virus was isolated by embryonated egg techniques and MDCK cells and identified by macro hemagglutination inhibition test, the antibody was detected by micro hemagglutination inhibition test. Results　The overall attack rate of influenza-like cases was 1.05% with much higher rate in women than in men. Higher attack rates were seen in two branches. Most cases were the people aged 15 years or above. All the 15 throat swab samples were nucleic acid-positive of A influenza viruses and one was nucleic acid-positive of H3 influenza virus. Two strains of H3N2 influenza viruses were isolated. As for the H3 influenza antibody detection, four-fold increasing of the antibody titers were observed in 9 serum samples of acute and convalescent phases (from the same patient). Conclusion　The outbreak was caused by H3N2 influenza virus. Intensified pathogenic surveillance is vital to control the epidemic.