The more controversial of two papers describing how the lethal H5N1 bird flu could be made easier to spread was published Thursday, six months after a scientific advisory board suggested that the papers’ most potentially dangerous data be censored.
The paper, by scientists at Erasmus Medical Center in the Netherlands, identified five mutations apparently necessary to make the bird flu virus spread easily among ferrets, which catch the same flus that humans do.
Only about 600 humans are known to have caught H5N1 in the past decade as it circulated in poultry and wild birds, mostly in Asia and Egypt, but more than half died of it.
The paper’s publication, in the journal Science, ended an acrimonious debate over whether such results should ever be released. Critics said they could help a rogue scientist create a superweapon. Proponents said the world needed to identify dangerous mutations so countermeasures could be designed.
“There is always a risk,” Dr. Anthony S. Fauci, the director of the National Institute for Allergy and Infectious Diseases, said in a telephone news conference held by Science magazine. “But I believe the benefits are greater than the risks.”
Two of the five mutations are already common in the H5N1 virus in the wild, said Ron A.M. Fouchier, the paper’s lead author. One has been found in H5N1 only once. The remaining two have never been found in wild H5N1 but occurred in the H2 and H3 flus that caused the 1957 Asian flu pandemic and the 1968 Hong Kong flu.
The Dutch team artificially introduced three mutations. The last two occurred as the virus was “passaged” through 10 generations of ferrets by using nasal washes from one to infect the next.
Four changes were in the hemagglutinin “spike” that attaches the virus to cells. The last was in the PB2 protein.
As the virus became more contagious, it lost lethality. It did not kill the ferrets that caught it through airborne transmission, but it did kill when high doses were squirted into the animals’ nostrils.
Fouchier’s work proved that H5N1 need not mix with a more contagious virus to become more contagious.
By contrast, the lead author of the other bird flu paper, Dr. Yoshihiro Kawaoka, of the University of Wisconsin, Madison, took the H5N1 spike gene and grafted it onto the 2009 H1N1 swine flu. One four-mutation strain of the mongrel virus he produced infected ferrets that breathed in droplets, but did not kill any.
New York Times