- Emerging data out of China ÷ the apparent birthplace
of SARS ÷ suggests the incubation period for the disease is longer
than has been believed, a spokesman for the World Health Organization said
today.
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- Health authorities in much of the world, including those
at the U.S. Centres for Disease Control, have pegged the average incubation
period for severe acute respiratory syndrome at two to seven days, with
some patients taking as long as 10 to fall sick following exposure.
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- Most infection control measures ÷ including those
employed against SARS in Canada ÷ are based on the premise that
someone who shows no sign of illness after 10 days is unlikely to come
down with the disease.
-
- But previously withheld case information from China has
led the WHO to rethink how long SARS can incubate before manifesting itself.
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- "The longest possible incubation period that we've
seen is 14 days," spokesman Dick Thompson said today in an interview
from Geneva.
-
- And 10 days? "That's what I would have told you
before we had access to the Guangdong data."
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- China's Guangdong province is believed to have been the
spawning ground for SARS. A doctor from Guangdong who attended a wedding
in Hong Kong is known to have triggered the infections that spread the
disease there and then to Canada, Singapore, Vietnam and several other
countries.
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- Despite the new information, Canadian public health officials
insist there is no need at this time to lengthen the period of isolation
imposed on thousands of people who may have been exposed to the virus by
contact with a SARS patient or by working at, being treated in or by visiting
two Toronto-area hospitals.
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- "I think if there were good reason to do it, absolutely,"
said Dr. Andrew Simor, head microbiologist at Sunnybrook and Women's College
Health Sciences Centre.
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- "But . . . it's a huge burden on people to say:
`We're still not sure, but let's increase it to 14 days.' I think there
are huge implications."
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- Dr. Donald Low, another key member of the SARS containment
team, said the evidence from the mounting number of cases in Canada suggests
most people develop symptoms within four to five days of infection, so
the 10-day period is probably safe.
-
- "We are seeing occasional patients ÷ and
that's occasional ÷ at 10 days. And . . . we feel confident of those
numbers," said Low, microbiologist-in-chief at Mount Sinai Hospital.
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- Ontario's commissioner for public safety said authorities
need to balance the risks against the practicalities ÷ or impracticalities
÷ of asking mass numbers of people to withdraw from society for
two weeks.
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- "We have to weigh our experience with what happens
in regards to obvious public safety but also people's needs to get on with
their lives and all of the other problems that are associated with isolating
large numbers of people," said Dr. Jim Young.
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- "We're not saying that wouldn't change. If our experience
began to show everyone developing symptoms in Day 9 and 10, we would likely
expand the isolation period. But that's not been our experience to date."
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