Surveillance of influenza in Honghe prefecture, Yunnan, 2006-2007

ObjectiveTo analyze the epidemic features of influenza in Honghe prefecture from 2006 to 2007 and discuss the changes of the predominant strains of influenza virus. MethodsThroat swabs derived from suspected influenza patients were inoculated into MDCK cells and cultured at 34 ℃ in a CO2 incubator for virus isolation. Hemagglutination test was then performed based on the culture medium, and serotyping was conducted for positive samples. ResultsA total of 911 throat swabs were collected in sentinel hospitals throughout the year and 123 strains of influenza virus were isolated (12.4%), among them 37 strains were H1N1 virus, 41 strains were H3N1 virus, 42 strains were B/Victoria lineage virus, one strain was B/Yamagata lineage virus and 2 strains were unspecified. A total of 56 swabs were collected from suspected patients by the centers for disease control and prevention in various counties and cities, and 39 strains of B/Victoria lineage virus were isolated (69.6%). ConclusionIn 2006, the predominant strain of influenza virus from March to June was B/Victoria lineage virus, and from July to September was H1N1 virus. In 2007, the predominant strain from January to March was H3N2 virus. All the strains isolated in suspected influenza epidemic were B/Victoria lineage virus.