The latest version is called H6N1, and represents the first time that this strain of bird flu has jumped from birds to people. Flu researchers are especially wary of birds, from wild avian species like migrating geese to run-of-the-mill chickens at local poultry markets. They harbor a series of influenza strains that generally don’t make the birds sick, but could cause serious disease in people if they jumped to human hosts. In recent years, more bird flu viruses that had never infected people before have been finding new human hosts. Last spring, for example, scientists in China reported the first human cases of H7N9 infections. These viruses previously circulated among birds, but mutations helped them to survive and sicken people as well.
Now, researchers in Taiwan say another avian flu strain, H6N1, may have made the jump as well. Scientists have described what they found when they analyzed a throat swab from a 20-year old woman who came to the hospital with shortness of breath and flu symptoms. When they sequenced the virus in her sample, they found it was very similar to H6N1 strains that have been found in chickens in the country since the 1970s, with one exception: this H6N1 had a mutation that gave it the ability to stick to human cells and gain entry, causing infection. Specifically, the mutation helped the virus to bind to cells in the human upper airway, a good place for viruses to attach after they are inhaled through the nasal passages.
The woman, a clerk in a deli who did not have direct contact with raw meats or poultry recovered. Scientists at the Centers for Disease Control (CDC) in Taiwan identified and tested 36 of her close contacts, including her brother, mother, neighbors, work colleagues and doctors who cared for her at the hospital. Only six had fever and respiratory symptoms similar to the woman’s; none showed signs of persistent infection with the virus. While it’s too early to tell how virulent H6N1 may be in people, the fact that this bird flu mutated and gained the ability to infect people is concerning, say public health experts. The development suggests that some of the H6N1 strains circulating among poultry in Taiwan now have the ability to make people sick. That’s an unstable situation, since additional mutations could make the virus either more dangerous to people or make it more innocuous; it’s all a matter of chance.
“As these viruses continue to evolve and accumulate changes, they increase the potential risk of human infection,” Dr. Ho-Sheng Wu, from the CDC in Taiwan. Coupled with the shift of H7N9 from birds to people last flu season, this latest case suggests that it makes sense to increase surveillance of the influenza strains circulating among birds for clues about the next potential viral flu threat.