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Biotech / Medical : SARS and Avian Flu -- Ignore unavailable to you. Want to Upgrade?

To: Biomaven who wrote (782)	5/11/2003 6:04:35 PM
From: Maurice Winn	Read Replies (1) \| Respond to of 4232

Peter, the picture of the bug shows it to be a big ball - if I remember rightly. It's about 10 to 20 times the diameter of a cold or flu virus. That makes its surface area 100 or 400 times bigger [dealing in very rough numbers here - surface area being 4 x pi x r2]. So, that would make it 100 times as slow in camouflaging itself via mutation. The previously infected person's immune system would see nearly all the old bits sticking out and would immediately call for the killer cells to get back on the job. I am making this up as I go and maybe immune systems don't work anything like my idea. Therefore, it won't come back to haunt people once they've recovered. Not for a few years anyway. Maybe actual biologists could say what really happens. Mqurice

To: Biomaven who wrote (782)	5/12/2003 1:16:57 AM
From: Torben Noerup Nielsen	Read Replies (2) \| Respond to of 4232

Peter, "You can get numerous colds because there are literally hundreds of different bugs that can produce cold symptoms" About half of all colds are caused by rhinovirus and you can be infected with the same strain repeatedly because there is very little adaptive immune response. A rhinovirus infection generally doesn't last long enough to fully stimulate the adaptive immune response. Thus memory B and T cells aren't produced in sufficient numbers to effectively prevent a subsequent infection even with the same strain. Rhinovirus is largely eliminated by the innate immune response and that doesn't have memory. Flu is problematic because it has a genome that consists of 8 separate strands. That allows reassortment during coinfection. Think of it as a form of viral sex; it allows for very rapid generation of variation. This is on top of mutation in individual strands of the genome. Torben