More similarities have been found between the bird flu creeping into Eastern Europe
and the 1918 Spanish flu that decimated populations worldwide, including the discovery of an entirely new way bird flu may kill human cells.
Researchers from St. Jude Children's Research
Hospital in Memphis, Tenn., have found that bird flu viruses carry a gene that can latch onto many crucial proteins inside human cells, presumably disrupting their function and causing far more severe disease than human viruses.
provides a new hypothesis for why certain bird flu viruses are particularly lethal for humans.
Published in today's issue of the journal Science, the research comes as Canada
prepares to release an updated pandemic flu plan that includes new infection control and border measures, from strategies to get people to wash their hands and cough into Kleenex, to surveillance systems in airports and emergency
rooms to detect the virus's introduction
There's no evidence so far that the H5N1 avian flu is transforming into the next human pandemic flu strain, but "we certainly are really increasing our efforts in terms of preparedness," says Dr. Theresa Tam, of the Public Health Agency of Canada.
But a SARS survivor, and infectious disease specialist, says Canada is "nowhere close" to being ready for a pandemic should it happen. Dr. Allison McGeer, of Mount Sinai Hospital in Toronto, says more money
and time needs to be spent on looking for new drugs for influenza, which masks will truly protect people, how sick people will be cared for when there aren't enough health-care workers and getting Canadians to agree on "fair and reasonable" distribution of vaccines.
In what is being described as the first large-scale mapping of bird flu viruses, researchers from St. Jude mapped 2,196 bird flu genes culled from ducks, gulls, shorebirds and poultry samples collected over 30 years, looking for patterns and comparing them to human flu bugs.
They also mapped the complete genome for 169 bird flu viruses. The work doubles the amount of genetic information available on avian flu.
The team honed in on a gene called NS 1. After looking at nearly 1,200 bird, human and swine NS 1 proteins, they found a particular feature of that gene which is unique in bird viruses and different from human ones.
In bird viruses, the gene produces a protein that allows the virus to bind to "scaffolding" proteins inside human cells.
"It's like a large number of policemen being held hostage. Society falls apart," says McGeer.
In human viruses, the protein doesn't bind to certain cells, which may explain why they're not as virulent.
It hasn't been proven yet. "But, we think that if you interfere with that many proteins in cells, you're going to have a deleterious consequences," said author Dr. Clayton Naeve of St. Jude.
The finding fits with what doctors on the ground in Asia
have seen: The H5N1 virus can attack not just the airways, like regular flu, but multiple organs and systems, including the kidney, liver, spleen and brain. Infection has been fatal in more than half the reported cases, and most cases occur in previously healthy children and young adults.
The H5N1 avian flu sweeping across Asia has this "bird" form of the protein. The milder pandemics of 1957 and 1968 had the "human" one.
The 1918 Spanish flu virus, which scientists now believe came from birds, had a very similar "bird" protein that the researchers believe behaves the same way. The protein could become a key target for the development of vaccines and new anti-flu drugs.
McGeer says the research answers "a big piece of the puzzle.
"Does it tell you H5N1 is going to be the next pandemic? No. What it does is add to our understanding of the evolution of influenza viruses."
Naeve says it is possible that whatever makes H5N1 so pathogenic, or toxic to humans, could persist even if the virus adapts to spread easily from humans to humans, and becomes pandemic.
If or when that happens is anyone's guess. Some virologists believe H5N1 is not going to be the next human pandemic.
The virus, which surfaced in Hong Kong
in 1997, has been in contact with humans for eight years "and we haven't seen the required mutation," says Dr. James Mahony, a professor of pathology and molecular medicine at McMaster University.
The 1918 virus, by contrast, jumped from birds to humans and was quickly lethal.
On Thursday, Indonesia
reported that a 22-year-old chicken seller infected with the H5N1 virus died, the country's 15th death from bird flu.
on Wednesday confirmed the country's 10th case of human infection with H5N1, a 29-year-old woman from Chengdu City in the province of Sichuan. It's not known if she was exposed to infected birds.
The virus has infected 152 people in six countries since 2003, killing 84 of them.
At least some species of migratory birds are carrying the virus to new areas along migratory flyways, according to a report presented this week to the WHO's executive board, and the chance the virus will spread to poultry in new areas "is now high."
Health officials in Canada are monitoring the outbreak of bird flu in Turkey, where two people have died. "To date, people are still convinced there is no efficient human to human transmission
," says Tam, associate director of the immunization and respiratory infections division at the Public Health Agency of Canada.
But, "we really have no idea how this virus will behave next if it undergoes some mutation."
The updated influenza pandemic plan will include recommendations for the use of masks. Droplets, or larger "blobs" of secretions primarily spread flu. General surgical masks should be enough should a pandemic happen, Tam says.
"Public health experts feel that putting a mask on an ill person when they're coughing or sneezing and have to move around ... is a sensible thing to do.
"Having well people milling about on the streets wearing masks all the time, we don't know if it's effective or not."
The public focus will be on hand hygiene, Tam says.