Posted on 08/19/2003 6:22:33 PM PDT by Brian S
By HELEN BRANSWELL
VANCOUVER (CP) - Theories abound but answers remain elusive as experts from Canada and beyond try to figure out whether a mysterious respiratory outbreak at a Vancouver-area nursing home - which claimed another life Tuesday - is a new and milder form of SARS.
The outbreak at the Kinsmen Place Lodge in suburban Surrey is confounding experts because most of the nearly 150 residents and staff who have become ill have suffered nothing more than mild cold-like symptoms - nothing like the severe disease that gave severe acute respiratory syndrome its name.
While public health officials in British Columbia insist the affected residents and staff do not have SARS, they do admit the virus that seems to responsible bears a perplexing similarity to the SARS coronavirus.
"If this is the SARS coronavirus, which is one possibility, we're definitely uncovering a different pattern of illness than the one described in the spring," Dr. David Patrick, director of epidemiology at the B.C. Centre for Disease Control, said at a news conference Tuesday.
"We know that this could be a mutated SARS coronavirus that has lost virulence and that's the favourite hypothesis among many people."
The news conference was called in an attempt to calm public concerns that B.C.'s Lower Mainland is seeing the first outbreak of SARS since the World Health Organization declared global transmission of the disease had ceased in early July.
The Surrey situation has drawn the attention of the WHO, which sent a virologist to the federal health lab in Winnipeg on Monday to examine the findings there in more detail.
"We are all in agreement that the illness associated with this outbreak is not SARS. It does not meet the case definition for severe acute respiratory syndrome," stressed Dr. Perry Kendall, provincial health officer for British Columbia.
"We haven't seen anybody with sort of atypical pneumonias that resulted in severe acute respiratory distress," said Dr. Roland Guasparini, medical health officer for the Fraser health authority, which is responsible for the Surrey area.
But the revelation of another death - in an elderly woman who died of pneumonia and who tested positive for the implicated coronavirus - may not help efforts to quell public concerns.
Guasparini noted her chest X-rays showed a typical pneumonia, not the atypical pattern that is found in SARS.
Since the outbreak began in early July, six residents of the nursing home have died of pneumonia-related illness.
Three tested positive for the coronavirus, using either polymerase chain reaction - or PCR - testing or by blood tests looking for antibodies to the SARS coronavirus. A number of residents and staff have also tested positive for the virus.
Both the B.C. Centre for Disease Control and Health Canada's National Microbiology Laboratory in Winnipeg have been trying to grow copies of the virus responsible for the outbreak so that they can compare its entire genetic code to that of the SARS coronavirus. To date those efforts have not borne fruit.
But labs in both facilities have been able to isolate pieces of the virus from specimens and have compared them to both the SARS virus and other known viruses that cause respiratory tract infections.
So far, findings from the Winnipeg lab point squarely at the SARS coronavirus.
"The segments of the genome that we've looked at which are now about 800 base pairs in fact are very close to SARS," said director Dr. Frank Plummer.
Patrick put that in context by pointing out the whole virus probably contains in the order of 30,000 base pairs - so only about one to two per cent of the genetic material of the virus has been decoded so far.
A portion of the virus that the B.C. CDC sequenced is actually a closer match for a known human coronavirus, he added. Plummer said the Winnipeg lab is trying to replicate that finding but hasn't completed the work yet.
"But our laboratory people are quick to tell us that these are preliminary findings. This isn't a section of the genome that alone would settle it and that we need a lot more work done," Patrick said.
"In other words, let's plunge into the other 98 per cent, please."
Plummer agreed. But he insisted that even at this early stage, the similarities to the SARS coronavirus are very striking.
"To me the two most likely possibilities are that this is some kind of mutant that's derived from the SARS coronavirus, because you wouldn't expect to see that much sequence homology (similarity) if they weren't derived from the same source," he said in a phone link from Winnipeg.
"Another possibility is it is the SARS coronavirus . . . but that we're seeing for some reason that we don't understand a very mild . . . illness."
Another theory was suggested Tuesday by SARS expert Dr. Donald Low, chief microbiologist at Toronto's Mount Sinai Hospital.
He wonders if the virus behind the Surrey outbreak is an old but previously unidentified human coronavirus that is closely related to the SARS coronavirus.
Until SARS was discovered, it was thought there were only three types of coronaviruses: one type that hit humans and was a cause of common colds; one that attacked birds and another branch that caused disease in animals such as mice, rats and pigs.
When the SARS virus was first isolated, researchers said it differed so significantly from all other known coronaviruses that it constituted a class of its own. But now Low wonders whether the SARS virus has some close cousins that no one identified before because there's little glory involved in isolating viruses that cause garden variety colds.
"Maybe there are strains of SARS (viruses) out there that have been around and have caused mild disease and nobody's really cared about identifying them in the past because they present as mild illness," Low said.
"What they're describing, maybe, is a whole family of coronaviruses that we now call SARS by default."
Whatever the explanation, Patrick stressed it won't likely come to light soon. "Sorting this out could take weeks."
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