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Posted on 03/31/2003 4:31:11 PM PST by Dog Gone

SCIENTISTS and health professionals have been gathering circumstantial data with which to predict the behaviour of the respiratory illness Sars. What seems like contrarian evidence has emerged, however, that could challenge assumptions and add a variation to its epidemiology.

The Hongkong health authorities are stumped by 92 cases reported in one day in a single apartment block in Kowloon, and are fearful it could mean the disease is air- or water-borne. If this is confirmed, or mutating viruses are implicated, the public-health threat could be far more serious than imagined. These 92 sufferers were among 213 confirmed cases in that housing enclave alone, up from seven only six days earlier.

Now contrast that with Singapore's experience. Epidemiological tracking here showed that prolonged close contact with sufferers accounted for almost all the known extended cases. The 'index' patients, original carriers of the Sars virus to enter Singapore, infected medical staff and family members with whom they came face to face. By cutting off suspected transmission routes through strict quarantine and turning Tan Tock Seng Hospital into a Sars emergency centre, Singapore has so far warded off random community outbreaks seen in Hongkong and Guangzhou.

Based partly on these episodes in Sars-affected areas in Asia and Canada, the World Health Organisation (WHO) put out a preliminary clinal alert that Sars was probably spread through droplets discharged through coughs and sneezes. Now, there is the air-borne imponderable to contend with.

Why do Singapore and Hongkong, both densely populated with similar high-rise living conditions, have different experiences? Are they more apparent than real?

This is where governments and inhabitants of affected countries need to keep an open mind about Sars. The United States Centres for Disease Control and Prevention (CDC), renowned for its microbe hunters, has picked up on the Kowloon case and is open to the probability of transmission through the air.

It has also left open the possibility that the suspected virus that could survive in air for a few hours would contaminate everyday objects in public places that people touch. That would be one more transmission vehicle. Singapore Health Minister Lim Hng Kiang's warning that the disease could be more contagious than thought should therefore be taken at face value. Thus far, it has been put about that an infected person is not contagious until symptoms appear.

One must hope scientists can be absolutely certain about this quickly, as much as they have to be certain whether or not Sars is also air-borne. The CDC for one acknowledges it just does not know if a person can spread the disease before symptoms appear, and how long the contagion may last - if at all - after a person has recovered fully.

These are sobering reminders that Sars could develop into an enduring mystery, with the consequences to match. Singaporeans are now much more respectful of Sars, as shown in much thinner weekend crowds and accepting quarantine restrictions without demur.

Those with pre-existing respiratory conditions (asthma, emphysema) ought to take especial care as a Sars infection could be more severe for them. On the prevention front, mainland China, Hongkong and Canada could complement Singapore's strict surveillance of air traffic to stop passengers with a Sars profile from boarding flights to and from their territories. WHO will have to make this an order sooner or later, beyond its general travel advisories.

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