Coronavirus causes SARS.
(This was also part of the article)
Posted on 12/18/2003 12:37:13 AM PST by FairOpinion
The Sars virus could be the result of a merger between viruses carried by birds and mammals, say researchers. The finding is based on a genetic analysis of the coronavirus, which causes the disease, and others that are closely related.
A similar phenomenon is responsible for the emergence of new types of flu virus.
The research, by a team from the University of Toronto, is published in the Journal of Virology.
Sars killed 774 people and infected as many as 8,000 in a world-wide outbreak earlier this year. China and Hong Kong bore the brunt of its effect, but Taiwan, Singapore and Canada also recorded many deaths.
The virus was eventually identified after a concerted international effort as a new kind of coronavirus.
Since our immune systems have never seen this new viral form, it is more difficult for them to respond to it in a timely and effective manner.
Professor David Guttman Such viruses usually cause a range of veterinary diseases - but usually nothing worse than the common cold in people.
Lead researcher Professor David Guttman, an expert in evolutionary genetics, found that about half the DNA in the Sars virus looked like coronavirus sequences taken from mammals.
But the other half looked liked coronoviruses normally found in birds.
And a key gene in the virus, known as the spike gene, seemed to be a mix of the two.
The spike gene is thought to control the virus' ability to infect cells.
Immune system fooled
Professor Guttman believes the merging of mammalian and avian viruses probably allowed the spike gene to sneak past the immune system defences.
He said: "These recombination events have the potential to create an entirely new structure essentially instantaneously.
"Since our immune systems have never seen this new viral form, it is more difficult for them to respond to it in a timely and effective manner."
Sars coronavirus was found in raccoon-like animals called civets in wildlife markets.
Professor Guttman said: "It's possible that a civet picked up the virus from a bird.
"This could have created the opportunity for a very rare recombination event that produced a virus with a new host range.
"Basically, the recombinant virus is infectious to humans, while the two parent viruses are not.
"This new virus likely then spread to humans due to poor hygiene and close quarters in the food markets of southern China."
Sars has not been seen since it was brought under control in June but health officials are watching warily for it to re-emerge.
Professor Guttman hopes his work will lead to more effective treatments.
Coronavirus causes SARS.
(This was also part of the article)
SARS emerged about a year ago, but the emergence was unrelated to the recombination, which happened thousands or millions of years ago.
Two colleagues of Taiwanese SARS patient are in America, official says
How can we be sure of that? If it's just the product of a very recent chance merger, might it not lack such an animal reservoir?
SARS CoV is NOT a recent merger. The merger is VERY old.
The sequences of SARS CoVs and other CoVs are readily available and there is no doubt that the differences between SARS CoVs and CoVs that cause colds and other respiratory diseases in animals are significant (with 20-30% homology). In contrast, the SARS CoV from masked palm civets or raccoon dogs are 99.8% homologous to the SARS CoVs from patients. These animal sequences represent the animal reservoir. Although it is possible that the sequences of virus isolated from live animal markets in Guangdong Province may be one step removed from the true reservoir, the sequence shows that any major recombination happened thousands or millions of years ago (which is why the homology with other CoVs is only 20-30%).
Antibodies in humans indicate that the jump from animals to humans was VERY recent (within the last year or two) and long after major recombinations among well studied animal CoVs. Moreover, animal traders with the highest frequency of SARS CoV antibodies are those that sell masked palm civets.
Thus, at a minimum, the civets facilitated the transfer of SARS CoV to humans, which is further supported with sequences from individual civet isolates.
I don't understand why the sequencing gives the date. I know glottochronology in linguistics depends on a demonstrably false assumption that languages change at a given rate.
The virus will mutate at a given rate. It has about 30,000 nucleotides. The animal coronaviruses in the study beginning this thread are only 20-30% homologous to SARS CoVs. In other words, about 20,000 of the 30,000 nucleotides have changed. This amount of change takes a long time.
The viruses representing the animal reservoir are 99.8% homologous. so there are only 50-60 changes. which happen in a much shorter time frame (the several months after the jump). Thus, the recent event involves viruses with a small number of changes. The recombinant event involves changes of 10's of thousands of changes.
In other words. the recombination had nothing to do with the recent jump, which involved an animal reservoir like that found in masked palm civets in Guangdong Province.
Wrong. The 29 nt are present in GZ01/GD01. The deletion is in the 8a/8b gene, not N.
The 29 nt deletion has nothing to do with the issue of recombination, which happened thousands or millions of years ago. The 29 nt deletion happened in 2003.
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