SARS is a coronavirus, a group of viruses that also includes some strains of the common cold. This means that SARS is probably likely to spread by the same vectors (mainly aerosol, with contact as a secondary vector). However, I saw a report yesterday that mentioned that although SARS may be related to the common cold, it doesn't appear to spread as rapidly as colds do. It seems that SARS is only transmitted through repeated contact with a sufferer, so just fleeting contact with a carrier (the "cough in the lift" scenario) is unlikely to result in the disease. If you think about it, Toronto has 300 known cases in a population of 2.5million, the chances of you meeting a carrier, let alone spending enough time with them to catch the disease, are slim at best!
One of the things it shares with cold viruses is its high mutation rate, so much so that samples of SARS taken from the discovery of the disease (less than 6 weeks ago) bear little resemblance to strains of SARS being found today.
If you think about it, we have maybe ten thousand max reported cases world wide, and out of that ten thousand a handful of deaths - so we have 0.0001% of the population, maybe resulting in say 5-10% of
that figure in deaths (I've just checked on the BBC news website, the known death toll is only 293 at the moment). Compared to diseases like malaria, TB, AIDS etc, that's just a drop in the ocean.
I'm not saying that we can be complacent with SARS, but you have to take it in context. People can die from influenza, but I don't see countries closing their borders because of flu. Although, come to think of it, it was about 100 years ago that we had the last major flu pandemic.
There are similarities between SARS and flu in that it appears to have started in the Far East (many flu epidemics can be traced back to the Far East, flu is virtually unique in that it can cross species boundaries, and in crossing those boundaries, picks up genetic variations, which results in new strains of flu. Flu epidemics are named by the point of origin, and the species of animal that the flu virus came from - although I have yet to see a Peking Duck flu strain
), and like flu causes distress in most of the population, but can be fatal in some cases. It's likely that SARS is a mutation of an animal form of coronavirus, that through mutation, has entered the human system.
The similarities between flu and the common cold mean that we'll probably never see a "panacea" vaccine for SARS - it mutates too quickly (the mutuations in flu, colds, AIDS etc. appear in the genes that encode the surface proteins, which means that any antibodies that an individual has against a previous strain of the disease are useless against any new strains).
Here's a useful link from the BBC, which gives some background.
Not to sound complacent yet, but at the moment there's not much to worry about. We really need to start worrying if it ever reaches the third world (at least if it stays in the first and seconds worlds, then at least these countries have the capabilities to treat and quarantine people. Third world countries do not have these capabilities, which means that the disease
could spread unchecked)...
Rgds
AndyF
PS - I knew the degree in Microbiology would come in handy someday. Never thought I'd use it on NTCompatible though
