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PandemicsThe pandemic potential of latest H7N9 flu strains

Published 27 October 2017

During China’s unprecedented fifth wave of H7N9 avian influenza activity, worrisome changes to the virus emerged, including a shift to a highly pathogenic form with some infections able to resist neuraminidase inhibitors such as Tamiflu, and now researchers who put the virus through its paces in animal studies are warning that the virus could easily become more lethal and resistant to treatment.

During China’s unprecedented fifth wave of H7N9 avian influenza activity, worrisome changes to the virus emerged, including a shift to a highly pathogenic form with some infections able to resist neuraminidase inhibitors such as Tamiflu, and now researchers who put the virus through its paces in animal studies are warning that the virus could easily become more lethal and resistant to treatment.

The novel virus first emerged in humans in China in 2013 as a low-pathogenic strain and remained fairly stable until the fifth wave, which was marked by a surge of infections across a much wider swath of the country that piled up more than 700 human infections as it killed poultry flocks for the first time. The case total in the fifth wave accounts for almost half of the global total of about 1,600 human cases.

The H7N9 virus is already at the top of the US Centers for Disease Control and Prevention’s (CDC’s) potential pandemic flu threat rankings, and in March, flu vaccine advisors to the World Health Organization recommended new candidate vaccine viruses be produced in case vaccines are needed against the latest circulating H7N9 strains.

CIDRAP says that in the new study, published in Cell Host & Microbe, a research team led by Yoshihiro Kawaoka, DVM, Ph.D., at the University of Wisconsin–Madison, conducted experiments in early 2017 to characterize and gauge the threat from a recent H7N9 sample isolated from a patient from China who died from the disease.

The main finding that has Kawaoka’s team worried is that for the first time they’ve identified a flu virus that spreads among ferrets and is lethal in both the animals experimentally infected and the ones kept in close contact, suggesting airborne spread. In a press release from the university, Kawaoka said, “This is the first case of a highly pathogenic avian virus that transmits between ferrets and kills them. That’s not good for public health.”

Earlier ferret studies on the low-pathogenic form of the H7N9 virus also found some evidence of airborne spread, but transmission didn’t appear to be as efficient.