WHO warns of a world-wide bird flu epedemic
(IHT.com)
Updated: 2005-09-17 15:16

"At this point H5N1 has pandemic potential, but it is not a pandemic virus," Thompson said, because it does not spread easily among humans.

But flu viruses are prone to mutation and exchanging genetic material when they co-infect an animal. One big fear is that an ordinary human flu virus and the bird flu virus could mix genes, creating a new type of lethal human bird flu virus, if they were present in an animal at the same time.

Because many viruses attack only certain species, this would most likely only occur in humans or pigs, scientists say.

But no one knows how likely this is. If it happened, the WHO estimates that it could kill 2 million to 7.4 million people worldwide. Others have made estimates in the tens of millions. Still, many are preparing for the worst. "It is not a matter of if, but when, avian influenza will strike Italy," said the Italian health minister, Francesco Storace, this week, in explaining Italy's purchases.

To prepare for the possibility of human bird flu, governments are racing to purchase the only two types of medicine known to have potential against the disease.

The first is a novel vaccine in the final stage of clinical tests. In tests, it elicits an immune response in humans against the A(H5N1) virus, but it takes two shots and requires a large dose, making it difficult to predict how well it would perform in the case of a sudden aggressive outbreak. The vaccine takes months to make, and all bets are off if the A(H5N1) virus variant that infects humans turns out to have changed substantially from the avian version.

The second strategy countries have employed is to purchase one of several antiviral drugs that are known to shorten the duration of influenza among those already infected and to reduce the likelihood of serious and deadly complications.

Treatment, however, must be started within 48 hours of infection. Also, they have shown only limited efficacy when they have been used to treat a few humans with bird flu in Asia, Thompson said, although they were mostly tried in people who were extremely ill.