The following is an excerpt.

A new bird flu virus that has killed 13 people in China is still evolving, making it hard for scientists to predict how dangerous it might become.

Influenza experts say the H7N9 strain is probably still swapping genes with other strains, seeking to select ones that might make it fitter.

If it succeeds, the world could be facing the threat of a deadly flu pandemic. But it may also fail and just fizzle out.

Read the full article here: Gene swapping makes new China bird flu a moving target