The United Nations health agency has begun trying to rapidly develop a vaccine against avian influenza - sometimes known as "bird flu" - after an outbreak that has claimed five lives in Hanoi, Viet Nam, in recent weeks.
The World Heath Organization (WHO) described the research into creating a vaccine as "a precautionary measure" following the outbreak, which has also decimated the bird population in Viet Nam, Japan and the Republic of Korea.
Officials at laboratories within WHO's Global Influenza Network are aiming to have prototype viruses for vaccine production ready for manufacturers within four weeks.
The highly pathogenic H5N1 avian influenza virus has been isolated from specimens taken from two of the recent fatal cases in Viet Nam, WHO said. Scientists are still determining how similar it is to the strain of the H5N1 virus identified in Hong Kong last year.