- (AFP) -- More than a year after its outbreak, experts
are still attempting to unravel the mystery behind SARS [Severe Acute Respiratory
Syndrome] and compounding the confusion is the latest suspected case of
the killer disease in China.
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- The pneumonia-like SARS, which surfaced in November 2002
killing nearly 800 people and infecting more than 8,000, is known to be
caused by a strain of the coronavirus, also responsible for the common
cold.
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- Although the epidemic was brought under control in July
last year, experts do not fully understand the behaviour of the virus that
originated in south China's Guangdong province.
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- What many believe is that SARS is caused by an animal
virus, but which animal is its natural reservoir or how the virus circulates
among the animal population remain a puzzle.
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- Scientists also do not know how the virus jumped the
species barrier from animal to humans, or whether the virus undergoes genetic
changes to escape detection.
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- There is also no foolproof diagnostic kit or cure yet
for SARS and the sole weapon against it is the centuries-old practice of
detecting and isolating those who are infected and those who came into
contact with them.
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- "Unless we have answers to all these questions,
it is difficult to prevent transmission from animals to human completely
or implement any specific control measures," Hitoshi Oshitani, the
World Health Organisation's (WHO) Manila-based regional adviser on communicable
disease surveillance and response, told AFP.
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- Dr Oshitani is currently helping to coordinate the WHO
probe into the status of a 32-year-old suspected SARS patient in Guangdong,
described as "an extraordinarily complex case" by the United
Nations agency.
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- The male television producer is the world's latest possible
case of the killer disease but experts are puzzled as to how he could have
contracted it.
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- Both Singapore and Taiwan have reported one confirmed
SARS case each since the epidemic petered out in July but the victims were
people linked to laboratory research on the virus.
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- "In this latest case, we don't have any clue how
he was infected and he doesn't have any risk factors or clear epidemiological
links," Dr Oshitani said.
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- "As far as we know, he didn't visit any laboratories
a few weeks before the onset of the disease, he didn't have any contact
with animals and also, the results on laboratory tests on him so far have
been inconclusive."
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- Dr Oshitani said initial tests had detected fragments
of a virus gene similar to the SARS virus in only one among several samples
taken from the patient.
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- Attempts to isolate and culture the whole virus using
the particular sample has failed.
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- "It is strange that only one sample is positive
and all others are negative," Dr Oshitani said.
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- Under such circumstances, the ominous prospect of a mutation
of the coronavirus or even laboratory contamination of the patient's samples
during testing have been raised but Dr Oshitani cautioned about jumping
to conclusions.
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- In another attempt to unravel the mystery, experts have
ordered a so-called virus neutralisation test on the patient.
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- Although described as the "gold standard" serological
examination for diagnosing any infection, the test is still constrained
by certain disadvantages for a dangerous virus like SARS.
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- "This new case only demonstrates that we still don't
have a proper diagnostic method that can easily identify or differentiate
between coronavirus infections from other infections," Dr Oshitani
said.
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- But even if the latest case is confirmed as SARS, many
questions would remain unanswered, he said, including whether the samples
were contaminated in the laboratory where the SARS virus is cultured for
research.
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- "We don't know how the patient was infected - that
is the most important question," he said.
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- If the contamination theory is ruled out, the authorities
have to find out whether the patient contracted SARS through human or animal
transmission.
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- The question of whether the virus originated from the
same animal population allegedly responsible for the epidemic last year
also has to be addressed.
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- Dr Oshitani said that if not for the efficient surveillance
system in China which managed to quickly identify and isolate the patient,
he could have become a source of a massive infection.
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- "This shows that the surveillance system established
after the epidemic last year is working and underlines the openness of
the Chinese government in sharing all information with us," he said.
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- © 2004 Australian Broadcasting Corporation
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- http://www.abc.net.au/news/newsitems/s1019939.htm
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