All the victims so far got the disease from poultry, but the big fear is that the virus could turn into a form capable of spreading from person to person.
A flu vaccine that might help prevent this will soon become available, but instead of going to Vietnam it will be sent to rich countries to fulfil existing contracts. And researchers who have created vaccines that might save us if the bird flu does start spreading between people are unsure how to proceed without falling foul of patent rights.
Doctors have been warning for years that another flu pandemic as deadly as the 1918 one is inevitable, and many worry it could be about to happen.
After an outbreak of the H5N1 strain of bird flu in poultry, Vietnam has reported 18 suspected human cases, 15 of whom have died. The World Health Organization has so far confirmed that five of the cases were caused by the H5N1 strain.
Unlike previous H5N1 outbreaks, the victims are mostly children. So far there is no sign of the bird virus spreading between people. But if someone is infected by H5N1 and a normal human flu virus at the same time, the viruses could recombine.
This might give rise to a new virus able to spread among people as easily as human flu but far more deadly, partly because it would bear the bird flu's H5 and N1 surface proteins, which human immune systems have not been primed to recognise.
To prevent this, the WHO wants to give the normal flu vaccine to everyone who might come into contact with sick poultry, as has been done in past outbreaks of bird flu.
The Belgian-based company Solvay, a major flu vaccine producer, is supplying the WHO with the vaccine used in the northern hemisphere this winter. But research published last week by the US Centers for Disease Control shows
Contact: Claire Bowles