- The deadly respiratory ailment SARS may have spread to
humans from cattle, just like mad-cow disease.
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- Scientists say the infectious agent they have identified
as the likely cause of severe acute respiratory syndrome is a previously
unknown coronavirus, one that some researchers say looks remarkably like
bovine coronavirus. In cattle, the common disease is known as "shipping
fever."
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- Coronaviruses ÷ which take their name from the
prominent "crown" of spikes clearly visible by electron microscopy
÷ occur in cattle, pigs, mice and humans.
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- The new pathogen may have crossed the species barrier
and mutated.
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- "It's hard to be definitive at this point, but it
can be hypothesized that it crossed the species barrier," Frank Plummer,
scientific director at the National Microbiology Laboratory in Winnipeg,
said in an interview yesterday.
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- He said he had examined the new coronavirus, which does
not yet have a name, under an electron microscope and "it somewhat
resembles several animal viruses. It's somewhere between a mouse corona,
a bird corona and cow corona."
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- Dr. Plummer said that many new diseases have jumped from
animals to humans in recent years, including HIV-AIDS, bovine spongiform
encephalopathy [commonly known as mad-cow disease and in humans, Creutzfeldt-Jakob
disease] and Ebola virus, often with deadly consequences. "As we change
the way we interact with our environment, these things are going to occur,
new diseases are going to emerge," he said.
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- While much of the attention of the scientific world has
focused on the new coronavirus, Dr. Plummer said it is necessary to keep
an open mind. In many of the samples analyzed, researchers have also found
metapneumovirus, which comes from a family of viruses that usually cause
respiratory ailments in children.
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- "At this point, we don't know if there are two separate
epidemics, or if these two viruses somehow work together to cause SARS.
There are still pieces of the puzzle missing."
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- Worldwide, there have been 1,485 SARS cases, including
54 deaths. In Canada, there have been 29 confirmed cases, including three
deaths.
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- World Health Organization officials now say that the
first known case of SARS occurred on Nov. 16, 2002, in Foshan, China. The
city is located in Guangdong province, an agricultural area where there
are large cattle farms. Guangdong is also a major supplier of food to Hong
Kong, which has been hit hardest by SARS.
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- The Canadian outbreak, however, has its origins in a
chance encounter in the elevator of the Metropole Hotel in Hong Kong on
Feb. 21 of this year. There, a Toronto woman and a Vancouver man crossed
paths with a professor from Guangdong who was infected with SARS.
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- Researchers now believe that professor was a "super-spreader,"
a modern-day Typhoid Mary who spread the disease readily to others. It
is well-established that some people shed viruses much more readily than
others, making them particularly infectious.
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- But viruses often lose their potency as they are passed
on to others, and that may explain why the disease may be becoming less
infectious and less deadly with each passing day.
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- After months of denial, China has acknowledged that the
unusual pneumonia epidemic that started there last November was indeed
SARS. It has just opened its doors to WHO investigators and it has agreed
to start releasing daily statistics, like every other affected country.
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- Like a common cold, SARS is spread by droplets, and appears
to be spread only by face-to-face contact. Virtually all the cases in Canada
are among family members of those originally infected and health-care workers
who treated them.
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- Containment measures, including quarantine of those affected
and those who may have come in contact with SARS in Toronto, have been
put into place to stop the spread of the disease.
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