Bird Flu Transmission: How Many Mutations Away?
The second controversial study about the potential spread of H5N1 bird flu to humans was released today, but those looking for conclusive answers about its transmission may be disappointed.
The studies focus on scientists’ efforts to show how virus strains could mutate, resulting in human-to-human transmission of the disease, instead of bird-to-human. The latter, while rare, can be fatal, but there are fears that mutations could eventually make it possible for humans to infect each other, raising the specter of an epidemic. More than 600 people have died from bird flu since 1997.
The first study, published in the journal Nature in May, used ferrets as models and found that the spread of the virus among humans probably wasn’t imminent. The New York Times reports that the second study, released today in Science, identified five specific mutations that may be required for the bird flu virus to spread among ferrets. Ferrets were used since they’re susceptible to the same flus as humans.
Two out of the five mutations already exist in virus strains, MSNBC says, and the other three could occur in infections of humans or animals, although the chances of that happening aren’t known.
An analysis of the studies in Science notes that in the first study, researchers created a hybrid virus by attaching a protein from an H5N1 strain to gene segments from the H1N1 virus. Although it took four mutations to make an airborne virus that was transmissible from one ferret to another, the hybrid hasn’t been found in nature.
In the second study, researchers started with a bird flu virus isolated from a human who contracted it. In tests, the virus was eventually able to travel through the air, infecting caged ferrets in close quarters.
However, in that form the virus didn’t kill the ferrets. Only when the virus was squirted directly into the ferrets’ nostrils did it prove deadly—but that’s hardly how the disease would be transmitted in humans.
Both papers almost never saw the light of day, thanks to concerns last December from the National Security Advisory Board for Biosecurity, which asked the journals Science and Nature to halt publication. The studies could provide too much information to bioterrorists, they claimed, sparking a huge debate within the scientific community.
But in March the NSABB relented after reviewing revised papers, and the first study was released.
“We now know we’re living on a fault line,” co-author Derek Smith of Cambridge University said in a news conference, the Associated Press reports. “It’s an active fault line. It really could do something.”
What do you think the chances are that there will eventually be a bird flu pandemic?