Posted on 04/02/2003 7:42:54 AM PST by CathyRyan
Canadian scientists racing to find the cause of SARS say it appears to be a mutant strain of coronavirus with bits of human, cow and mouse virus scrambled into its genetic code.
In a study rushed to publication in the New England Journal of Medicine yesterday, the scientists said five of six Toronto SARS patients tested positive for the virus.
In an editorial, the journal's editor suggested the new virus --whatever it is -- be named Urbani, in honour of Dr. Carlo Urbani, the World Health Organization physician who defined SARS and who died of the disease last week.
The Canadian study also cast doubt on the possibility the virus is airborne. Its patterns suggest droplet or contact transmission.
Some researchers believe the virus jumped the species barrier near Foshan, in China's Guandong province, where the first SARS cases were reported. The province's 90 million people live in close proximity to livestock, including cattle and ducks, creating an ideal environment for viruses to thrive and mutate.
"An educated guess? It's probably a mammal coronavirus that has jumped onto some human beings at some point and is now spreading." said co-author Raymond Tellier, director of medical microbiology at the Hospital for Sick Children in Toronto.
"The behaviour of the disease suggests a virus out of equilibrium with its new situation. It's the kind of behaviour that one would see when you have a virus that jumps species."
Most established viruses don't kill their hosts, or they can't survive, said Dr. Tellier. But when strains jump the species barrier, they can be fatal, as the Ebola virus is when it breaks out in human populations. Coronavirus is not the only suspect, however. Last month, scientists in Canada, Germany and Hong Kong also found traces of human meta-pneumovirus in SARS patients.
But some researchers doubt that it could be causing SARS. They believe large segments of the general population may carry it without getting sick. The fact it turns up in SARS patients could be a coincidence.
"Although it was first recognized last year at a lab in the Netherlands, we think [human meta-pneumovirus] has probably been around for a long time," said co-author Robert Brunham, director of the University of British Columbia Centre for Disease Control.
Dr. Brunham said human metapneumovirus has been shown to cause respiratory illness, but nothing as serious as the symptoms of SARS.
However, scientists would not rule out the possibility that both human metapneumovirus and coronavirus could be involved together. Coronavirus is known to suppress the immune system, which could lower the body's defences against human metapneumovirus.
Although diseases that require the presence of two viruses are rare, they do exist.
For example, hepatitis D virus cannot replicate in the human body without the presence of hepatitis B virus.
Portions of the new virus resemble a coronavirus that afflicts cows, giving them a runny nose, a condition sometimes called "shipping fever." Other portions resemble a coronavirus found in mice, which gives them hepatitis. Finally, portions resemble the coronavirus that causes the common cold in humans. Together, they appear to cause SARS.
Although the symptoms of SARS vary from mild to fatal, scientists do not think the virus is changing as it races into the human population.
"We got about five isolates and they don't seem to be mutating at the present time," said Dr. Brunham.
Researchers say the best way to determine why the virus is behaving as it does is to sequence its genome, which contains about 30,000 base pairs. With the right equipment and safety precautions, this could be done in a single day, something scientists hope to accomplish soon.
bevenson@nationalpost.com
SARS likely a mutant strain of human and animal viruses Scientists publish study: Researchers say virus is probably not airborne
Would the combination of the three occur naturally, without human intervention?
Recombinants like this are very common in nature.
Usually, however, they are fatally impaired by the recombination. It is unusual-but not necessarily suspicious-that such a recombinant became more, not less, pathogenic.
| Time | Number of cases | Percentage increases | Number of current deaths as a percentage of case totals on previous days | |||||||||||
| Day | Date | New | Total | Day | Week | Deaths | Today | Day ago | 2 Days | 3 Days | 4 Days | 5 Days | 6 Days | Week |
| Wed | 03/19 | 150 | ||||||||||||
| Thu | 03/20 | 23 | 173 | 15.33% | ||||||||||
| Fri | 03/21 | 30 | 203 | 17.34% | ||||||||||
| Sat | 03/22 | 19 | 222 | 9.36% | ||||||||||
| Sun | 03/23 | 25 | 247 | 11.26% | ||||||||||
| Mon | 03/24 | 13 | 260 | 5.26% | ||||||||||
| Tue | 03/25 | 26 | 286 | 10.00% | ||||||||||
| Wed | 03/26 | 30 | 316 | 10.49% | 110.67% | |||||||||
| Thu | 03/27 | 51 | 367 | 16.14% | 112.14% | |||||||||
| Fri | 03/28 | 58 | 425 | 15.80% | 109.36% | |||||||||
| Sat | 03/29 | 45 | 470 | 10.59% | 111.71% | 10 | 2.13% | 2.35% | 2.72% | 3.16% | 3.50% | 3.85% | 4.05% | 4.50% |
| Sun | 03/30 | 60 | 530 | 12.77% | 114.57% | 13 | 2.45% | 2.77% | 3.06% | 3.54% | 4.11% | 4.55% | 5.00% | 5.26% |
| Mon | 03/31 | 80 | 610 | 15.09% | 134.62% | 15 | 2.46% | 2.83% | 3.19% | 3.53% | 4.09% | 4.75% | 5.24% | 5.77% |
| Tue | 04/1 | 75 | 685 | 12.30% | 139.51% | 16 | 2.34% | 2.62% | 3.02% | 3.40% | 3.76% | 4.36% | 5.06% | 5.59% |
| Wed | 04/2 | 23 | 708 | 3.36% | 124.05% | 16 | 2.26% | 2.34% | 2.62% | 3.02% | 3.40% | 3.76% | 4.36% | 5.06% |
| Averages | 11.79% | 119.58% | 2.33% | 2.58% | 2.92% | 3.33% | 3.77% | 4.25% | 4.74% | 5.24% | ||||
And if so, what do you make of this?
BTW, thanks for this info.
HONG KONG (Reuters) - The first victims of the deadly new virus spreading across the world were people in China's southern province of Guangdong who ate or handled wild game, the South China Morning Post reported on Thursday.
A top health expert in China said the earliest patients of the flu-like Severe Acute Respiratory Syndrome (SARS) in Guangdong had close and continuous contact with chickens, ducks, pigeons and owls, the newspaper said.
"We will explore further if the disease was passed to human beings from wild animals. You know, Guangdong people like eating exotic animals and I don't find it a healthy practice," said Bi Shengli, a vice director at the Chinese Center for Disease Control and Prevention (news - web sites).
The earliest cases of the disease were traced to either chefs or bird vendors, Bi said.
The deadly virus is thought to have originated in southern China. Carried by travelers to Hong Kong, Vietnam, Singapore, Canada and other countries, the virus has killed 78 and infected 2,313 people so far. Many of those infected have since recovered.
Mainland China and Hong Kong account for most of the cases. The World Health Organisation and a growing list of countries have stepped up measures to keep the disease at bay and have warned people against traveling to affected areas.
The virus comes as a huge blow for Hong Kong, which has had to grapple with what has now become annual attacks of a "bird flu," a deadly avian virus that jumped the species barrier to humans in 1997. It infected 18 people, killing 6 of them.
It's not known how that avian H5N1 virus jumped to humans.
Experts say SARS has nothing to do with H5N1, but they have not ruled out the possibility that it could be linked to other bird or animal viruses.
Scientists in Hong Kong say the SARS virus comes from the family of coronaviruses, which causes the common cold.
They say such viruses can originate from animals, although SARS looks nothing like any known human or animal virus.
However, the newspaper said Bi did not believe SARS had anything to do with coronaviruses.
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