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Missed opportunity?

Yvonne Chan

Shortly after the re-emergence of Sars in China, the public was warned of the return of another deadly disease: bird flu. Experts sounded the alarm after it was suspected to have claimed the lives of more than a dozen people in Vietnam. South Korea has culled more than 1 million birds since last month in an effort to contain the disease and Japan this week reported its first avian flu outbreak in chickens in almost 80 years. Taiwan has killed 20,000 chickens as a precautionary measure.

The World Health Organisation has expressed worries that bird flu could be a bigger threat to humans than Sars. Officials in Vietnam suspect the virus spread to pigs before infecting humans.

The WHO believes it may only be a matter of time before the bird flu virus attaches itself to a common human flu strain, facilitating human-to-human transmission - and thus a global pandemic.

Statistically, bird flu has proved more deadly than Sars. In 1997, avian flu killed six of 18 infected Hong Kong residents - a death rate of 33 per cent. The death rate of local Sars cases was 17 per cent. Of the suspected cases in Vietnam, 13 of 18 people have died.

There is no human vaccine for bird flu - a disease so virulent that it causes the body to attack itself, causing multiple organ failure in the worst cases. However, a vaccine for the H5N1 virus - the strain identified in the 1997 bird flu outbreak in Hong Kong and found to have caused the epidemic in Vietnam - might already exist if not for a decision by the WHO six years ago. An article in the South China Morning Post in 1998 reported that a team of WHO experts in Geneva had ruled out an H5N1 threat and advised against the production of a vaccine.

The organisation stated: 'At present, it is not justified to make recommendations for the production of an influenza A H5N1 vaccine for general use,' citing a lack of evidence of the spread of the deadly strain beyond Hong Kong.

If the experts in Vietnam are found to be correct in their theory that H5N1 spread to pigs before being transmitted to humans, it should not come as a surprise to the medical community. Many experts believe the worst flu epidemics - such as the 1918 Spanish flu and the 1968 Hong Kong flu - originated as bird flu before spreading to humans via pigs. These days, bird flu - perhaps unfairly and inaccurately - has been viewed overseas as an endemic disease, with its roots in Hong Kong.

Most of Hong Kong's live chicken supply comes from mainland farms which are not subject to the biosecurity measures put in place locally after the 1997 outbreak. There has been speculation that the H5N1 in Vietnam originated in Hong Kong. Taiwan - which has been affected by the less virulent H5N2 strain - is investigating the possibility that smuggled poultry products from mainland China may be the source.

Just as travelling humans spread Sars from the mainland to overseas countries, so migratory birds and shipments of farmed chickens may be found to have spread the avian flu virus outside China.

Last year's Sars outbreak demonstrated the deadly impact animal-borne viruses have on the global population, and a global effort is now underway to develop a H5N1 vaccine. Hong Kong Medical Association President Lo Wing-lok believes that 'even if an H5N1 vaccine was developed in 1997, the chances are the viruses detected in 2004 would have already mutated, making the 1997 vaccine no longer useful'.

Yet there remains the question of why it was thought the source of the 1997 bird flu outbreak in Hong Kong could not happen elsewhere. Given the limited information at the time, the oversight was understandable. But if a vaccine - which may or may not be helpful today - had been produced, the medical community would have at least been able to glean knowledge from the experience.

Yvonne Chan is an editor on the Post's newsdesk

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