A 20-year-old woman in Taiwan is the first person known to be infected with a strain of bird flu called H6N1, according to a new report of the case.
In May, the woman was hospitalized after she developed a high fever, cough and shortness of breath. Tests for common respiratory infections came up negative, but more detailed tests revealed she had H6N1, a flu virus that's common in birds, but has never before been seen in people.
The woman was treated with the anti-viral medication oseltamivir (Tamiflu), and made a full recovery. [10 Deadly Diseases That Hopped Across Species]
So far, there's no evidence that H6N1 can spread between people. Of the 125 cases of flu reported in Taiwan since the woman became ill, none were caused by H6N1. The researchers also tracked down 36 people who came into contact with the woman, six of whom became sick around the time she did, but there was no indication they had H6N1.
It's not clear how the woman became infected with the virus. She worked in a deli, and did not have close contact with chickens or wild birds.
H6N1 is the latest bird flu virus to hop over to humans. Earlier this year, the first human infections with the H7N9 bird flu virus were reported in people in China. The H7N9 virus has since sickened 139 people, including 45 who died, according to the World Health Organization.
The new finding "shows the unpredictability of influenza viruses in human populations," the researchers, from the Taiwan Centers for Disease Control, wrote in the Nov. 14 issue of the journal The Lancet Respiratory Medicine.
Further studies are needed to better understand the potential threat posed by H6N1, including research that investigates how the virus passes from animals to people, the researchers said. The findings also highlight the need for continued surveillance for new flu viruses, the researchers said.
An analysis of H6N1 genes showed that the strain found in the woman is similar to those seen in chickens. However, through a genetic mutation, the virus appears to have evolved the ability to bind to human cells in the upper respiratory tract.
Further genetic changes in the virus could increase its ability to pass from chickens to people, or from person to person, the researchers said.
Given how common H6N1 is in birds, and that several other types of bird flu viruses are known to cross over to people, it could have been anticipated that an H6 flu virus would eventually appear in people, said Dr. Richard Webby, a bird flu expert at St. Jude Children's Research Hospital in Memphis, Tenn., who was not involved in the new study.
The big question is whether the genetic mutation in H6N1 means that it will now infect more people (causing an outbreak), or if the current report is just a sporadic case, Webby said.
"All of these viruses are, of course, a concern," Webby said. The new finding means that health officials will view H6N1 as slightly more risky, in terms of its pandemic potential, than they did in the past, Webby said.
The woman's case was reported by Taiwanese officials in June, but the new study is the first detailed report of the case.