PARIS: A mutated bird flu virus that has killed six people in China displays worrying traits that warrant high vigilance, experts say, though the true extent of the threat is unclear.
Most concerning is the virus' wide geographical spread, and the fact that it seems to be spreading unseen among its host animals, possibly chickens or ducks.
"I am cautiously worried," virologist John Oxford of the Queen Mary University of London told AFP.
"If there were four cases in Shanghai, I would be much less concerned, but because it is so geographically widespread I think it is trying to tell us something.
"It is not a deadly virus for chickens so it could spread in chickens without anyone knowing it. I suspect it's probably wider than we think."
Having made its jump from animals to humans, which required a series of genetic mutations, the influenza A(H7N9) strain has now been diagnosed in four Chinese provinces: Jiangsu, Zhejiang, Anhui and the business capital Shanghai.
Of 14 people confirmed infected, six have died since February. Patients suffer from severe pneumonia with a fever, cough and shortness of breath.
Bird flu strain has regional ramifications
