THURSDAY, Feb. 23 (HealthDay News) -- The avian flu, which
killed almost 60 percent of those known to be infected, actually
struck many more people worldwide but didn't make them very sick, a
new analysis finds.
The actual fatality rate of the H5N1 flu strain, therefore, is
probably less than 60 percent considering that millions of people
may have been infected over the past eight years, the researchers
The analysis results confirm earlier findings, said one expert,
Dr. Marc Siegel, an associate professor of medicine at New York
University. It's still not clear how fatal the strain actually is,
but the research "emphasizes that H5N1 is not as deadly in humans
as is being proposed by some people," said Siegel, author of
Bird Flu: Everything You Need to Know About the Next
Siegel added that he doesn't think "this particular virus is
going to mutate to go easily from human to human. That's extremely
Scientists and public health officials have been sounding the
alarm for years about the potential that the avian flu strain
called H5N1 could become a major threat to humans. As of last
December, the World Health Organization (WHO) reported a total of
573 cases since 2003; of those, 59 percent died.
Fears about the strain are so intense that a controversy erupted
this year over whether scientists might help bioterrorists by
publishing details about their research into bird flu. The WHO
agreed last week to allow the research, which examines a mutated
and more contagious form of bird flu, to be published.
In the new report, researchers from Mount Sinai School of
Medicine in New York City launched a combined analysis of 20
studies that examined blood test results from than 12,500 people.
They found that 1 percent to 2 percent of them had signs that
they'd been infected with the H5N1 infection. Most of those said
they hadn't recently had cold or fever symptoms.
The research suggests that few people are being infected by the
strain, Siegel said. It would be unusual for this particular type
of flu to mutate in a dangerous way that could cause it to become
contagious between people, he said.
Philip Alcabes, a professor of public health at City University
of New York's School of Public Health at Hunter College, cautioned
that the findings do show that the strain infects people more
easily than previously thought.
"Does this mean H5N1 is more or less of a threat to human health? Really, the report changes nothing in that regard -- because the public health concern about avian flu is about the possibility of future change in the virus-human relationship. With this study we know a little more about the present virus-human relationship -- but we still don't have a crystal ball," Alcabes said.
"So it remains important to understand how animal viruses, including H5N1 and others, circulate among animals and how they migrate to human populations," added Alcabes, who was not involved in the new study.
The analysis appears in the Feb. 23 online issue of
For more on
pandemic flu, try the U.S. National Library of Medicine.
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