Dual infections by influenza A/H3N2 and B viruses and by influenza A/H3N2 and A/H1N1 viruses during winter 2007, Corsica Island, France.

BACKGROUND: The investigation of dual influenza infection human cases is of major interest specifically for the control of new emerging influenza strains.
OBJECTIVES: Using RT-PCR assays, we retrospectively assessed the prevalence of dual influenza virus infections that occurred in patients during the 2006-2007 winter season in Corsica Island (France). STUDY
DESIGN: One hundred and thirty-four nasal swabbing samples taken from patients suffering from influenza-like illness between February and March 2007 were analysed using a rapid influenza antigen detection test, cell culture and RT-PCR assays. RESULTS AND
CONCLUSION: Influenza viruses were detected in 93 (69.4%) of 134 patients with influenza-like illness using the combination of classical and molecular assays. Dual respiratory infections by influenza viruses were detected in 3 (3.2%) of the 93 influenza positive patients, including two cases of infection by influenza A/H3N2 and B viruses and one case of dual infection by influenza A/H3N2 and A/H1N1 viruses. In the present report, human co-infection cases by two influenza viruses appeared as a rare event in symptomatic patients. However, the virological and epidemiological mechanisms that determine the occurrence of dual influenza infections remain to be fully investigated in further prospective multicentric studies.