Coping with the coming pandemic in poultry

Gwynne Dyer, London

The long-term solution is to invest many billions of dollars and a huge amount of political capital in persuading peasant families throughout China and Southeast Asia to change the way they raise their poultry. The urgent short-term task is to develop a way of mass-producing influenza vaccine far faster than is now possible. It's urgent because "the world is in the gravest possible danger of a global pandemic," as Shigeru Omi, Western Pacific regional director of the World Health Organization, told an emergency conference on avian flu held in Vietnam two months ago.

The H5N1 avian flu virus first crossed into human beings in 1997, but it has clearly been mutating in recent years in ways that make it more capable of moving from birds to people. The spate of human infections in mid 2003 in China and Southeast Asia was so serious that over 100 million domestic birds were killed or died in those countries before it subsided in early 2004, but there was only a few months' respite before bird-to-human transmission began again last June.

The virus has now appeared in wild birds who can carry the virus far beyond its original reservoir in domestic chickens in southern China and Southeast Asia: In late May China closed all its nature parks after 178 migratory geese were found dead from the virus in Qinghai province in the north-west. The most recent outbreak has so far killed 53 people in Vietnam, Thailand and Cambodia -- and even more ominously, the first probable case of human-to-human transmission was recorded last September in Vietnam.

The danger of a global flu pandemic that could be as bad as or worse than the "Spanish influenza" outbreak of 1918-1919 (which killed 40 to 50 million people, half of them young, healthy adults) comes from the fact that a strain of influenza virus that normally affects only birds can swap genes with a strain that is highly infectious between human beings. If people with the human type of influenza should also be infected with the avian type (through direct contact with infected poultry), the gene swap can easily occur -- and direct human-to-human transmission becomes possible. At that point, given current patterns of international travel, the world might be only weeks away from a global pandemic.

We don't know if avian flu viruses swapping genes with human types caused the lethal Spanish influenza, but that was certainly the source of the much milder "Asian flu" outbreak in 1957-1958 (which killed 70,000 people in the United States alone) and the "Hong Kong flu" pandemic in 1968-1969 (50,000 US deaths). Given the rate at which influenza viruses mutate, we are overdue for another pandemic -- and this one could be a monster.

The H5N1 virus is resistant to most anti-viral drugs, and in the avian form it has been getting steadily stronger. Early outbreaks killed around 10 percent of poultry flocks; more recent ones have been killing up to 90 percent.

In people who have caught avian flu, the death rate has been horrendous: 50 to 75 percent of those infected. A gene-swapped version that is directly communicable between human beings might be less lethal, but it could still far exceed the 1-2 percent fatality rate of the Spanish influenza. To make matters worse, this version of avian flu has a long incubation period. Unlike the SARS virus that killed 774 people two years ago, it may be very hard to stop before it spreads into the general population.

"When people were transmitting the (SARS) virus they were already showing signs, so it could be picked up at airports with temperature (detectors)," explained World Health Organization spokesman Peter Cordingley. "With (avian) flu you can be infectious before you show any signs." If human-to-human infections start to spread, there could be not only huge loss of life, but global economic chaos as air travel is shut down to contain the spread, borders are closed, and essential services break down because too many of their workers are off sick or just hiding from the flu at home.

Governments are already arming themselves to deal with this pandemic -- on April 1 President George W. Bush added "influenza caused by novel or reemergent influenza viruses that are causing, or have the potential to cause, a pandemic" to the list of diseases for which a quarantine can be declared -- but there is no vaccine. As things stand now, none could be available for months after the pandemic begins. That is why five teams of scientists, writing in last week's edition of the journal Nature, urged a permanent global task force to react quickly to outbreaks of bird flu. If it is not done, they warned, millions will die.

The first opportunity to create such a task force will be at the G-8 summit in Scotland next month, and its first priority must be to develop new and easily produced vaccines to deal with the expected outbreak. But lasting progress, as Samuel Jutzi of the UN's Food and Agriculture Organization said at the Vietnam meeting in March, depends on "addressing the transmission of the virus where it occurs, in poultry, specifically free-range chickens and wetland-dwelling ducks." In other words, a couple of hundred million Asian peasants have to be persuaded to stop living in the same space as their poultry. A tall order, but a necessary one.

The writer is a London-based independent journalist.