Key quote:

"The first time an avian flu virus was found to have infected people
was in Hong Kong in 1997. At least 18 people fell severely ill and six
died.

Experts believe a pandemic may have been averted that time by the
rapid slaughter of Hong Kong's entire poultry supply — an estimated
1.5 million birds killed in three days.

That flu virus was the H5N1 variety, one of 15 known subtypes of avian
flu. The WHO calls it worrisome for several reason: It mutates rapidly
and tends to acquire genes from flu viruses in other animal species;
it is clearly dangerous to people; and it spreads quickly. Infected
birds give off the virus for at least 10 days in their feces and oral
secretions.

H5N1 appeared again last February, when two members of a family
returning to Hong Kong from China became ill. One died and the other
recovered."


By DANIEL Q. HANEY, AP Medical Editor

With luck, the world will escape the latest outbreak of bird flu with
no more than the six human deaths already blamed on it and the loss of
millions of chickens. But public health experts worry of a much
greater disaster: A catastrophe they say is among the worst
imaginable, a global outbreak of an entirely new form of human flu.

There is no clear sign that will happen. Nevertheless, avian
influenza's sudden sweep through Asia, along with its tendency for
wholesale mutation, leave many wondering about the bug's potential for
rampant spread among humans. It is a possibility the medical journal
The Lancet calls "massively frightening."

"The question everybody is asking is, 'Is this the progenitor to a
pandemic?'" says Dr. Gregory Poland, chief of vaccine research at the
Mayo Clinic.

Influenza pandemics typically strike three or four times a century.
The worst in the past 100 years, the 1918-19 Spanish flu, caused an
estimated 40 million to 50 million deaths. Another is considered
inevitable and perhaps overdue, but when it will happen and how bad it
will be are almost totally unpredictable.

The nightmare this time would be a flu virus leaping from birds to
people and spreading, introducing a disease for which humans have no
natural defense.

The potential source is the strain of bird flu that has moved rapidly
through parts of Asia since December, infecting chickens in at least
six countries.

Millions of birds have died of the flu or were destroyed by workers
trying to contain the outbreak. The World Health Organization says
eliminating this "animal reservoir" is urgent.

Avian flu is naturally carried by wild ducks, and it ordinarily does
not attack creatures other than birds or pigs, so experts are
especially concerned that this bird flu is occasionally infecting
people.

Human cases have been reported in Vietnam and Thailand, including six
deaths as of Saturday in Vietnam, the WHO said, and one suspected
death in Thailand. Experts believe all caught the virus from chickens,
not other people.

"We know there are two possible ways a new pandemic strain can
emerge," said Dr. Steve Ostroff, deputy director of the National
Center for Infectious Diseases at the Centers for Disease Control and
Prevention (news - web sites). One is a human flu virus that
resurfaces after years of dormancy, so people have no defense built up
from earlier bouts. The other is a non-human variety acquiring the
ability to infect people and spread.

The latter may happen if somebody already infected with a human flu
virus also catches the bird virus. Inside the body, these two may
recombine into a new mutant, part-human virus, part-bird.

The more people are around infected chickens and other birds, experts
say, the more chances there are for such a disaster to occur.

"If the virus continues to spread in chickens, it may adapt itself so
it can grow in humans," says Dr. Arnold Monto, a University of
Michigan epidemiologist. "If it is transmitted human to human, then we
are concerned this is the start of the great pandemic."

The first time an avian flu virus was found to have infected people
was in Hong Kong in 1997. At least 18 people fell severely ill and six
died.

Experts believe a pandemic may have been averted that time by the
rapid slaughter of Hong Kong's entire poultry supply — an estimated
1.5 million birds killed in three days.

That flu virus was the H5N1 variety, one of 15 known subtypes of avian
flu. The WHO calls it worrisome for several reason: It mutates rapidly
and tends to acquire genes from flu viruses in other animal species;
it is clearly dangerous to people; and it spreads quickly. Infected
birds give off the virus for at least 10 days in their feces and oral
secretions.

H5N1 appeared again last February, when two members of a family
returning to Hong Kong from China became ill. One died and the other
recovered. How and where they got infected was never learned.

The disease now circulating in Asia is the same H5N1, but it is so
widespread that a quick purging, like Hong Kong accomplished seven
years ago, is unlikely. Testing shows it has mutated but has not yet
picked up any genes from human flu viruses.

If a bird flu pandemic occurs, could it be stopped? Many experts fear
not. Flu is so contagious that quarantining victims, a method that
eventually contained SARS last year, is unlikely to work.

Studies suggest that prescription drugs used to treat human flu
strains could also keep people from catching the bird flu. However,
spot shortages were reported during this winter's U.S. flu outbreak,
and supplies would quickly run out during a pandemic. No country has
stockpiled the drugs, Tamiflu, Relenza and the older amantadine and
rimantadine.

The WHO is already working on a prototype vaccine against the bird
flu. But even the standard annual flu shot takes six months to
manufacture, and experts doubt a new vaccine could be ready in time.

If there is evidence the bird flu is producing significant illness in
humans, "there would be a full-bore effort to produce a vaccine," says
the CDC's Ostroff. "It's hard to predict the timeliness of it and how
widely it could be put into people's arms."

___

EDITOR'S NOTE: Medical Editor Daniel Q. Haney is a special
correspondent for The Associated Press.

HONG KONG (Reuters) - Scientists in Hong Kong have discovered people
with a certain pattern of genes have a much higher risk of getting
SARS, a finding that could help diagnose and prevent the spread of the
deadly disease.

A study of SARS patients in Hong Kong showed individuals with a
pattern known as HLA-B*0703 were four times as likely to contract the
respiratory disease, said Paul Chan, an associate professor in
microbiology at the Chinese University of Hong Kong.

Those with a pattern labeled HLA-DRBI*0301 had a much lower risk,
indicating genetic make-up may play a key role in determining if some
people are more susceptible to the virus than others.

"Our findings from this study will help us more accurately diagnose
the disease and design effective prevention programs," Chan said on
Thursday.

"For example, we could test an unproven vaccine or prevention method
on the high-risk group. Hospitals may also consider sending only
low-risk health workers to take care of SARS patients," he said.

The Hong Kong researchers examined the blood samples of 90 SARS
patients and studied the patterns of their human leucocyte antigen
(HLA) genes, which influence the activity of cells that are
responsible for the immune system's response during infections.

The results were then compared with samples from people who did not
have Severe Acute Respiratory Syndrome.

More than 1,700 people in Hong Kong contracted SARS last year after it
spread from southern China and nearly 300 of them died. Worldwide,
more than 8,000 people were infected and more than 800 died.

China recently announced its first confirmed SARS case in months and
two suspected SARS cases in the southern city of Guangzhou. The
government is still awaiting definitive test results on the suspected
cases.

Another Hong Kong scientist said on Wednesday it was a new variety of
the SARS virus that had emerged in China and it appeared to be less
contagious than the strain last year.

Both are believed to be from the same family of coronaviruses, which
also cause the common cold.


By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - A genetic susceptibility may explain why SARS
raged last year in southeast Asia and nowhere else in the world
outside of Toronto, Taiwanese researchers reported this week.

They found a certain variant in an immune system gene called human
leukocyte antigen, or HLA, made patients in Taiwan much more likely to
develop life-threatening symptoms of SARS.

The gene variant is common in people of southern Chinese descent, the
team at Mackay Memorial Hospital in Taipei reported.

Their finding, published in an online journal, BMC Medical Genetics,
must be confirmed by independent researchers. But the Taiwanese team
said the genetics could explain the puzzling distribution of SARS last
year.

"After the outbreak of SARS coronavirus infection in the Guangdong
Province of China, it was surprising to observe that the spreading of
the disease was mostly confined among southern Asian populations (the
Hong Kong people, Vietnamese, Singaporeans and Taiwanese)," they
wrote.

Severe Acute Respiratory Syndrome first arose in Guangdong last
November. It spread to Hong Kong, Vietnam, Beijing and Singapore, and
was transported around the world by airliner. SARS eventually was
suspected of affecting 8,098 people and killing 774, according to the
World Health Organization's latest figures.

The flu-like disease is caused by a virus from a family known as
coronaviruses. They cause diseases in livestock and some cases of the
common cold in people.

The SARS coronavirus is unique genetically but similar versions have
been found in animals sold in Chinese food markets.

Marie Lin, Chun-Hsiung Huang and colleagues examined the HLA gene in
37 cases of probable SARS, 28 fever patients excluded later as
probable SARS, and 101 non-infected health care workers who were
exposed or possibly exposed to SARS coronavirus.

"An additional control set of 190 normal healthy unrelated Taiwanese
was also used in the analysis," they wrote in their report.

They found that patients with severe cases of SARS were likely to have
a version of the HLA gene called HLA-B 4601.

They noted that no indigenous Taiwanese, who make up about 1.5 percent
of the population, ever developed SARS. HLA-B 4601 is not seen among
indigenous Taiwanese, they noted.

"Interestingly, (HLA-B 4601) is also seldom seen in European
populations," they added.