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Pastimes : SARS - what next? -- Ignore unavailable to you. Want to Upgrade?

To: Maurice Winn who wrote (599)	6/25/2003 10:19:40 PM
From: Henry Niman	Read Replies (2) \| Respond to of 1070

>>Colds are really small viruses, so can hide better and they have a vast pool of infection in which to mutate<< WRONG. 30% of colds in humans are caused by coronaviruses, which are the largest known RNA viruses. Not coincidentally, a SARS coronavirus is a coronavirus. Coronaviruse, like most RNA viruses have the ability to mutate VERY rapidly because their polymerase gene does have a proof reading function and the virus easily recombines because of their mode of replication through sub-genomic RNAs. Class II coronavirus even have part of the hemagglutin gene from flu viruses (which are also RNA viruses). SARS coronaviruses already have picked up the 3' stem loop region from astroviruses (also RNA viruses). The human immune system will be quite busy trying to deal with all the tricks the virus has up its sleeve. That is why people get colds many times over the years. The immunity to one coronavirus produces limit immunity against another. Coronaviruses mutate once every 10,000 nucleotides. Since the SARS cornavirus is 30,000 nucleotides in size, it averages 3 mutations each time it replicates.

To: Maurice Winn who wrote (599)	6/25/2003 11:07:57 PM
From: Henry Niman	Respond to of 1070

>>But I admit that I don't know quite what an RNA virus is and just how many changes of clothes the sars bug can do over a few years<< I think your time frame is a bit off. I haven't seen all of the data, but looking at presentation slides suggests that the virus emerged in Nov 2002. By Feb 21, 2003 the virus in the Metropole Hotel had already had a 29 nt deletion and 7 Metropole Hotel linked stable mutations which have been found in all published sequenced isolates traced to the Hotel. The isolates were from Toronto, Bangkok, Hong Kong, Singapore, Taiwan, and Shenzhen (and it seems likely that the mutations would also be in mainland China outbreaks seeded by 23 passengers on flight attendants on Air China flight CA 112 which went from Hong Kong to Beijing on March 15, 2003. The virus is probably silently spreading via mild and/or asymptomatic cases. I think you will be in for a MAJOR surprise when cold/flu season returns in the fall/winter.