H7N9 is the 'nastiest virus in humans in years'
1 May 2013 Last updated at 16:14 BST
The outbreak of a new type of bird flu in China poses a potentially serious threat to human health according to scientists.
The H7N9 outbreak emerged a month ago and so far more than 100 people have been infected and there have been 24 deaths.
Crucially the virus is not able to spread between people, which would be needed if it was to become a new flu pandemic.
Our medical correspondent Fergus Walsh spoke to Professor Wendy Barclay from Imperial College London.