Amid ominous signs that H5N1 bird flu is acquiring the ability to spread more readily among people, many health authorities are pinning their hopes on Tamiflu, the only available antiviral drug known to block the replication of the virus. But can the drug really help stop an emerging flu pandemic?

Even if efforts to develop a vaccine are successful (New Scientist, 26 March, p 10), it could take many months to produce the billions of doses needed in the event of a pandemic. By then it might be too late. So in the meantime, the World Health Organization is stepping up its efforts to acquire a massive stockpile of Tamiflu (oseltamivir), which it hopes will at least slow any emerging flu pandemic.

Recent cases of H5N1 in northern Vietnam have caused concern because of signs that the virus is changing. It has become less lethal and is occurring in larger clusters than past cases. Last month studies also revealed that the virus is diverging genetically.

Tamiflu can save lives if it is given early, no more than two days after symptoms first appear. But last month the WHO reported that a patient in Vietnam had a strain of H5N1 resistant to Tamiflu. So could the drug become useless before the pandemic even begins?

This article continues in www.newscientist.com

Copyright ? The New Scientist