Thursday, May 01, 2003

Two British experts on SARS

I attended an evening seminar on Tuesday given by Professor Roy Anderson and Professor John Oxford. These are my notes on their comments (not verbatim):

Roy Anderson

There are four reasons why we might expect more reports of global epidemics in the future:

1. New infections are identifiable as being distinct.
2. There is greater mixing of people from different countries.
3. Population size, and more importantly, population density, is increasing.
4. Bigger cities - not just more people living in cities, but more really big cities.

Most new infections arise from pathogens that transfer to humans from animals. Therefore, areas of the world where people live in close proximity to each other and animals are more likely to give rise to them e.g. China and India.

There are three main tasks to be undertaken when a new infection arises:

1. Identify the pathogen and sequence its genetic structure. From this, we can produce diagnostic test, both for the live virus and for indication of exposure.
2. Develop a method of treatment.
3. Control the spread via public health measures, like isolation and quarantine, to prevent secondary transmission.

In relation to point 1, work on this has been extraordinarily quick. In turn, isolation and quarantine has worked well. It is on the question of treatment where there has been little success. While there are technical problems to be overcome in relation to this, there is an important question of regulation to be looked at. If a treatment can be developed quickly, should it still need to go through all the steps for approval that are currently required? If so, it would significantly delay its application.

How serious is SARS? It has not been the disaster expected in some quarters. It is very pathogenic, causing death in about 11 percent of cases. However, it seems to have poor transmission qualities. Therefore, it is containable in those countries already affected.

John Oxford

One question that has arisen in relation to SARS is infectiousness. What is an infectious virus? Is SARS going to spread?

One way of understanding the complexity of the question is an analogy with tropical plants. If you were to go on holiday and saw a plant you liked, you might bring it home only to find that it died. Some organisms that do well in one environment do not do well in other environments. So, SARS may not 'take' in Europe.

Another aspect is the ease of spread. For example, in a crowded room like this, someone coughing who had influenza would be very likely to pass it on to everyone else. Measles is a similarly infectious disease. On the other hand, SARS, like smallpox, could only be contracted from close contact with an infected person. Ballroom dancing is a good illustration of what close contact means: being face-to-face with someone, or physically touching them.

SARS seems to have brought out the best and worst of people. The best is illustrated by the courage of Carlo Urbani, the WHO officer in Viet Nam who stayed to investigate the new disease he had found, even though he was risking his life in doing so (and subsequently died as a result). On the other hand, we have the Chinese academic, knowing he was infected and knowing the consequences, who ran to Hong Kong, knowing of the likelihood of infecting others.

Those doctors that have cancelled their conference in Toronto have not set a good example, in this regard.

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