Gene Difference May Explain SARS Epidemic

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.