Study: New bird flu strain could cause pandemic

CHICAGO — Lab experiments on a new strain of the H7N9 bird flu circulating in China suggest the virus can transmit easily among animals and can cause lethal disease, raising alarm that the virus has the potential to trigger a global human pandemic, researchers reported Thursday.

The H7N9 virus has been circulating in China since 2013, causing severe disease in people exposed to infected poultry. Last year, human cases spiked, and the virus split into two distinct strains that are so different they no longer succumb to existing vaccines.

One of these also has become highly pathogenic, meaning it has the ability to kill infected birds, posing a threat to the poultry industry.

U.S. and Japanese researchers studied a sample of this new highly pathogenic strain to see how effectively it spread among mammals, including ferrets, which are considered the best animal model for testing the transmissibility of influenza in humans.

In the study published in Cell Host and Microbe, flu expert Yoshihiro Kawaoka of the University of Wisconsin and colleagues tested a version of the new H7N9 strain taken from a person who died from the infection last spring.

They found that the virus replicated efficiently in mice, ferrets and non-human primates and that it caused even more severe disease in mice and ferrets than a low pathogenic version of the same virus that does not cause illness in birds.