ABSTRACT
Objective To observe epidemic status and the types of the influenza virus, to analyse influenza epidemic trends in Tianshui City, and to provide basis for influenza prevention and control. Methods Throat swab specimens of influenza cases in pilot hospitals and area of influenza-like a typical outbreak in Nov. 2005-Oct. 2008 was tested by chicken embryo and MDCK cells.The identifi cation of the isolates was carried out by hemagglutination and hemagglutination inhibition test. The separation of strains were sent to the National Influenza Center to conduct a review appraisal. Results 1819 throat swab specimens of influenza-like were collected and 247 were isolated. Isolation rate was 13.58%. There were 36 strains (14.57%) of A (H1N1) subtype, 75 strains (30.36%) of A (H3N2) subtype and 136 (Victoria department 121, Yamagata department 15) strain (55.06%) of B subtype. Conclusion There were three epidemic types of influenza virus types-A (H1N1), A (H3N2) and B in Tianshui. Virus were epidemic at the same time or alternating at different intensity in different years. Outbreaks of influenza have occurred in rural primary and secondary schools, and B subtype was dominating.