While H7 influenza viruses do not historically generate pandemics or undergo human adaptation, several unusual properties of the viruses suggest they may be different from other avian influenza viruses, bringing into question any assurance that the likelihood of human adaptation is low, according to a paper published in mBio, the online open-access journal of the American Society for Microbiology.
The publication describes the history of H7 viruses in animal and human disease, pointing out that H7 influenza tends to become established in bird, horse, and swine populations and may spillover repeatedly into humans.
“In attempting to assess the possible risk of an H7N9 pandemic, it is important to consider not only AIVs [avian influenza viruses] in general but also specific H7 influenza outbreaks that may give us clues about what to expect from H7N9,” the authors wrote. “In this regard, the evidence as a whole is complex and the implications of past outbreaks for predicting the future course of the current H7N9 epizootic are uncertain.”
Several highly unusual traits of these viruses, including their poultry epizootic potential, mammalian adaptation, and atypical clinical syndromes in rarely infected humans, paint a “disquieting picture” of a pathogen that may hold the potential for a pandemic, according to lead scientists from the National Institute of Allergy and Infectious Diseases: David Morens, Jeffery Taubenberger, and Anthony Fauci.