New bird-flu strain in Asia found resistant to vaccines
A new strain of bird flu in Asia is resistant to the vaccines being used to protect poultry against the disease, and scientists are less certain that this virus poses no threat of spreadingdirectlybetweenhumans.
“The predominance of this virus [among birds] over a large geographical region within a short period directly challenges current disease control measures,” scientists at the University of Hong Kong, who discovered the new viral strain, said inareportinProceedingsoftheNational Academy of Sciences.
Karen Lacourciere, program officer for the National Institute of Allergy and Infectious Disease, said the “rapid spread” of the H5N1 virus the researchers described in their report was “surprising.”
“It was a powerful paper the way they made their point that we must detect this early on, so we can appropriately adjust our interventions and preparedness for a pandemic,” she said.
Dr. Yi Guan and the other authors of the report are not ready to dismiss the possibility that the new virus can spread directly between humans, rather than only from birds to humans, a development that would make a major human epidemic possible. The new virus has produced 22 confirmed human infections in 14 Chinese provinces since November 2005.
“Some of those cases were residents of metropolitan areas remote from poultry farms [. . . ] furthermore,therewerenoobviouspoultry outbreaks reported to neighboring markets or farms before or after theonsetofthosehumaninfections,” the Chinese scientists wrote. “Therefore, whether those people were infected locally and directly from affected poultry, or other sources, including humans, is still unknown.”
Dr. Yi and his colleagues said their surveillance of live-poultry markets and the use of genetic testing indicate the “emergence and predominance” of the “Fujianlike” H5N1 strain over other avian-flu viruses.
This development of resistance “maybeassociatedwithvaccination in poultry,” they observed.
Mrs. Lacourciere said it’s too earlytoknowwhetherthisnewbirdfluvirusmightcauseamajorhuman epidemic, but she thinks there may “eventually be a pandemic.” Because the Fujianlike strain is “dom- inant in China and Southeast Asia,” surveillance of the strain is needed in those places, she said.
Brian Epstein, a spokesman for the World Health Organization (WHO), said on Oct. 30 that he had not yet read the report but advised against panicking about the Fujianlike H5N1 virus.
Hesaidthevariantseemstosidestep current vaccines against avian fluinpoultryandthat“meansmore chickensmaybesusceptible”tothis form of avian flu, “but it does not necessarily mean more people will get it.”
“There is bird flu all the time. Thesevirusesconstantlychangeand mutate.Thisdoesnotmeanitwillbe transmitted to humans,” he said.
While some argue there have been no known cases of human-tohuman transmission of H5N1, the authors of the new report cited recent “suspected cases of human-tohuman transmission involving members of an extended family in Indonesia.”
The authors of the NAS report further held that genetic testing showed the Fujianlike virus was responsible for the “increased prevalence of H5N1 in poultry since October 2005 and recent human infection cases in China.” This has occurred, they said, even though China has required flu vaccination of all poultry for more than a year.
What’s more, they said, the Fujianlike virus “has already caused poultryoutbreaksinLaos,Malaysia and Thailand, and human diseases in Thailand.”
In 2005, WHO confirmed 97 human bird flu cases in eight Asian or African countries and 42 deaths infiveofthosenations.ButasofOct. 16, the agency said, 109 human casesalreadyhadbeenconfirmedin nine nations and 73 deaths in eight of them.
Deadly or delightful? A bird sits on a wire in Greenwich, Conn. on Oct. 31.