Misidentification of Diphyllobothrium Species Related to Global Fish Trade, Europe

Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 20, No. 11, November 2014 1955 virus infections in Hangzhou (online Technical Appendix Figure). Prompt control of A(H7N9) infection outbreaks and vaccination against seasonal influenza viruses could reduce the potential for co-infections with A(H7N9) virus and seasonal viruses. Taken together with the previous finding of human co-infection with A(H7N9) virus and A(H3N2) virus (1), our results show that human coinfection with A(H7N9) virus and each of the 3 seasonal influenza viruses currently circulating worldwide can occur. Avian influenza viruses, including A(H7N9), preferentially replicate in the lower respiratory tract of humans (8,9). In contrast, seasonal influenza viruses preferentially infect the upper respiratory tract of humans (10). Coexistence of A(H7N9) virus with either A(H1N1)pdm09 virus or influenza B virus in the pharyngeal swab samples from 2 patients suggests that the upper respiratory tract could provide a location for the A(H7N9) virus to reassort with other influenza viruses. The possibility that seasonal influenza viruses might provide some gene segments that increase the human-to-human transmissibility of possible new reassortants is cause for concern. For detection of such new influenza virus reassortants, extensive surveillance to identify influenza virus co-infections is necessary.