Investigation on mixed infection of pandemic H1N1 and seasonal H3N2 Viruses

Abstract

Objective To understand the epidemiological characteristics in an outbreak of mixed infection of H1N1 and H3N2 viruses through analysing the clinical features,antibody changes,pathogenic detections and to provide basis for the disease prevention and control measures.Methods Epidemiological and clinical data were collected by in-terviewing patients and retrieving medical records.Viruses were identified by RT-PCR assays followed by sequence analy-sis.Hemagglutination inhibition(HI)test was used to detect antibodies for both viruses.Results In 45 people with influenza-like illness,40 were laboratory-confirmed influenza cases,among which 22 were infected by pandemic H1N1virus,12 by seasonal H3N2 virus,and 6 by both viruses.The clinical manifestations of patients with different virus infection were essentially similar.There was no substantial difference in genomic sequences of either pandemic H1N1 or seasonal H3N2 virus between patients with the mixed and single infection.Sequence analyses revealed that all the detected viruses were oseltamivir-sensitive but adamantane-resistant.HI tests of paired sera confirmed the mixed infection within the outbreak.Conclusions Co-circulation of both viruses lead to a mixed infection influenza pandemic.However,pandemic H1N1 virus is priority in prevalence in the course of transmission. Key words: Influenza A virus,H1N1 subtype; Influenza A virus,H3N2 subtype; Outbreak; Infection; Epidemiology