Asian bird flu reveals Australian vulnerabilities

Despite contingency planning, Australia remains highly vulnerable to an influenza pandemic should the deadly strain of avian influenza burning through Asian poultry farms mutate to a form capable of direct human-to-human transmission.

Dr Alan Hampson, head of the Australian Influenza Reference Laboratory of the World Health Organisation (WHO), said there was no vaccine against a virulent new mutant of the H5N1 serotype of the influenza A virus -- and it would take at least five months to develop one.

And two international pharmaceutical companies that manufacture anti-influenza drugs that protect against all known forms of the influenza virus today told Australian Biotechnology News that they would not have sufficient supplies to cope with the overwhelming demand that would occur if a pandemic strain reached Australia.

Prof Peter Colman, of the Walter and Eliza Hall Medical Research Institute in Melbourne said yesterday few Australians were aware that there were two very effective drugs -- Relenza and Tamiflu -- that could prevent influenza, or reduce the severity and duration of an established infection.

Colman, whose work was instrumental in the development of Relenza, said it was very likely that their unique action would make them effective against the new strains, and any new pandemic strain that might emerge from Asia.

Colman said that in the absence of a protective vaccine, the anti-influenza drugs should at least be made available to people "in the firing line" -- workers involved in chicken culls or, in the event of a pandemic, front-line medical workers like doctors and nurses.

In a bulletin issued yesterday, the World Health Organisation said the new H5N1 strain might have "unique capacity to cause severe disease, with high mortality, in humans".

Since mid-December, near-simultaneous outbreaks of avian influenza in Vietnam, China, South Korea, and Thailand, have killed millions of chickens and forced the mass-slaughter of millions more. Thousands of workers involved in the cull are unprotected, either by vaccine or the world's most effective anti-influenza drugs, GlaxoSmithKline's Relenza and Roche's Tamiflu, increasing the risk of more human infections.

New problem

The fact that the new H5N1 serotypes are highly lethal to chickens raises a new problem. Since early last century, vaccine makers have used embryonated chicken eggs injected with emergent flu virus strains to produce attenuated-virus vaccines.

Not only are H5N1 serotypes lethal to adult chickens, they also kill embryonated eggs, making it impossible to produce a vaccine by the conventional route. US health authorities have funded a program to develop new ways of producing vaccines, including vaccines produced by genetic engineering.

While scientific evidence indicates that the new strain, and the original Hong Kong strain, can only move between birds and humans, and not between humans, genetic recombination between the avian flu and human-infecting strains could creating a virulent hybrid capable of direct human-to-human transmission.

But recombination may not even be required to create a pandemic strain.

In a research article published several years ago, renowned Australian influenza expert Prof Robert Webster, of St Jude Children's Research Hospital in Memphis, Tennessee, said the worst pandemic of the past two centuries, the so-called Spanish flu of 1918-19, probably involved an avian influenza virus that 'jumped' unchanged to humans, probably via pigs. At least 20 million people on six continents died in the pandemic, and another 200 million were infected.

Research has shown that both the H5N1 strain that killed six out of 18 people infected in the 1997 Hong Kong outbreak, and the new strain now killing chickens and humans in Vietnam, are almost identical to a strain now widespread in farmed chickens and ducks throughout Asia.

The WHO is concerned that as large numbers of people become exposed to the strain during the mass-cull of chickens in Asia, there is a greater risk that a new recombinant or variant strain will emerge that will be capable of human to human transmission.

Australian Biotechnology News understands that the contingency plans for an influenza pandemic in Australia include a small emergency stockpile.