GENEVA - The reservoir of H7N9 virus and its transmission mode in China could be the two most important points for the ongoing investigations and the risk of epidemic is low given the current evidence, said a spokesman for the World Health Organization (WHO) Wednesday.

Gregory Hartl, media officer for WHO, reconfirmed that to date, the organization has no evidence of human-to-human transmission and the source of the infection is still an open question.

Hartl declared that given the current evidence, the seven confirmed cases China had reported by the time he made the remarks "are unlinked, with no epidemic logical between the cases."

"Without human-to-human transmission, the risk of epidemic is low, and WHO has no plan to establish an emergency committee yet," said the spokesman.

He pointed it out that mutation has been identified in the virus, a change believed to allow the virus to infect humans.

Hartl added that labs collaborating with WHO are doing the cross-reactivity test to see how well the existing vaccines for other influenza type work against this new virus.

Up to now, H7N9 bird flu cases reported by China has risen to nine.