Lottery win more likely than bird flu
By Mark Henderson, Science Correspondent
THE chances of a British person falling ill with avian flu will be as low as 1 in 100 million even if the virus infects birds in Britain, the Government’s chief scientist said yesterday.
While the spread of the H5N1 virus to Europe is a serious issue for farming and wildlife, it presents a negligible threat to human health that should not worry the public, Professor Sir David King told The Times.
Speaking after a further 11 wild birds in France were confirmed yesterday to have tested positive for H5N1, bringing the country’s total to 29, Sir David said that the experience of the disease in Asian countries suggests that individuals are about seven times more likely to win the national lottery than they are to contract bird flu.
In China, where the disease is endemic among birds, just 14 infections and 8 deaths have been confirmed by the World Health Organisation in a population of 1.3 billion people — a rate of one case per 93 million and one death per 163 million.
This suggests that the current form of the virus is so difficult for humans to catch that the risk will remain extremely remote even if it infects British birds, as is likely now it has spread to France and Germany.
Britain’s population is 60 million, making even a single case unlikely at these odds.
Speaking exclusively to The Times, Sir David said that the public health threat from the virus had been widely exaggerated, and confused with the danger it posed to the poultry industry.
“It is very important to keep things in proportion, and to make a distinction between the virus in birds and the virus in humans,” he said.
“Your chances of winning the lottery are about 1 in 14 million. Your chances of catching bird flu are more like 1 in 100 million, even if we had H5N1 among the chicken population in Britain.
“That’s a back-of-the-envelope calculation based on China, but the real figure will not be much different. It may in fact be even lower than 1 in 100 million, because we don’t live cheek-by-jowl with chickens in the same way. Simply put, this is not an issue we should worry about in terms of public health.”
He said that Britain was right to prepare carefully for a potential flu pandemic, but that the discovery of H5N1 among European birds had made this no more likely. From a human health point of view, he is more concerned about the spread of H5N1 into Africa, where cases have now been confirmed in birds in Egypt, Nigeria and Niger.
These developing countries lack the resources to contain the disease, and have backyard poultry flocks similar to those found in the Far East, which expose large numbers of people to the virus. This creates potential crucibles for genetic mutations that could allow the virus to start spreading from person to person, a critical event for a pandemic.
“The situation for Africa is going to be considerably harder to handle than the situation in China,” Sir David said.
His comments were backed by Neil Ferguson, Professor of Mathematical Biology at Imperial College, London, one of the world’s leading influenza epidemiologists. He said that the risk of human cases in Britain was “absolutely negligible”.
“There have been about 150 infections in South-East Asia and China, and the population size of the heavily affected region is around the 300 to 400 million mark,” Professor Ferguson said. “Whether it is 1 in 100 million or 1 in 10 million, it is a very small risk. I really don’t think H5N1 in Britain poses any public health risk. British people don’t have contact with birds in the same way as in Asia. We don’t have live poultry markets or kill the birds we eat at home. We buy our chicken cold, and there are safeguards to stop infected meat getting into the food chain. The risk is absolutely negligible, though convincing people of that is difficult because H5N1 has now acquired a rather mythological status.”
DEWEY RESPONDS:
The source is a government scientist. Perhaps by telling the story this way, he can calm the English.
The key component in the math of this bet is this paragraph:
“It is very important to keep things in proportion, and to make a distinction between the virus in birds and the virus in humans,” he said.
The odds were figured on the current unevolved virus. If H5N1 evolves from a "virus in birds" to a "virus in humans," all these kinds of bets are off. That is what the world scientists fear. If it just stays a bird flu, it just kills the poultry industry and a few of the poor people who work with chickens. So it is nothing to be worried about.
Of course, we are still not really cheerful to see our birds here at the lake threatened with death. We were sad when the merganzer of the broken wing disappeared one day. We were hoping the poor crippled fella would make it until spring. Some hawk is probably pretty happy, however.
The real gamble, however, is the bigger one. The more birds spread H5N1 around among themselves, the more chances it has to evolve or recombine into a human to human flu. Then, since it is so new to our immune systems and so deadly, it kills about 50% of us, well less of us old folks really, when you factor in it killing about 90% of those who are under 40.
In spite of the odds, because they sell enough tickets, someone eventually wins the lottery. If we think of the numbers of viruses living and breeding in world bird populations as lottery tickets, it is not unreasonable to believe one of those viruses will win (through evolution or recombination) the ability to pass from human to human.
And here the lottery analogy really breaks down. When the lottery winners win, they do not ever spread that money around to all the rest of us. If the H5N1 wins and becomes lets say S227N (click on this- it may have happened today), many more of us get to share in the winnings.
Of course, I suppose the bet is still a safe one because if the flu evolves, it will no longer be called H5N1 but some other number like S227N, so technically the dead people could not collect their bets. It is one of those tricky bets where the devil is in the details.
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