H7N9: preparing for the unexpected in influenza.
In the years prior to 2013, avian influenza A H7 viruses were a cause of significant poultry mortality; however, human illness was generally mild. In March 2013, a novel influenza A(H7N9) virus emerged in China as an unexpected cause of severe human illness with 36% mortality. Chinese and other public health officials responded quickly, characterizing the virus and identifying more than 400 cases through use of new technologies and surveillance tools made possible by past preparedness and response efforts. Genetic sequencing, glycan-array receptor-binding assays, and ferret studies reveal the H7N9 virus to have increased binding to mammalian respiratory cells and to have mutations associated with higher virus replication rates and illness severity. New risk-assessment tools indicate H7N9 has the potential for further mammalian adaptation with possible human-to-human transmission. Vigilant virologic and epidemiologic surveillance is needed to monitor H7N9 and detect other unexpected novel influenza viruses that may emerge.
Influenza Division, National Center for Immunization and Respiratory Disease, Centers for Disease Control and Prevention, Atlanta, Georgia 30329; email: dbj0@cdc.gov , njc1@cdc.gov.
Daniel B
DB
Jernigan
Nancy J
NJ
Cox
D002681:China / Q000453:epidemiology; D006801:Humans; D064766:Influenza A Virus, H7N9 Subtype / Q000235:genetics / Q000472:pathogenicity*; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology*; D020545:Respiratory Mucosa / Q000378:metabolism; D012720:Severity of Illness Index; D014779:Virus Replication / Q000235:genetics
emerging infection; preparedness; risk assessment; sequencing