LONDON, Apr 20: The new strain of bird flu that has killed 17 people in China has been circulating widely “under the radar” and has acquired significant genetic diversity that makes it more of a threat, scientists said yesterday. Dutch and Chinese researchers who analyzed genetic data from seven samples of the new H7N9 strain say it has already acquired similar levels of genetic diversity as much larger outbreaks of other H7 strains of flu seen previously in birds.