Risk of bird flu spreading to cows outside US: WHO

"With the virus carried around the world by migratory birds, certainly there is a risk for cows in other countries to be getting infected," said Wenqing Zhang, head of WHO's Global Influenza Program at a news briefing in Geneva.

She reiterated that the UN agency deems the overall public health risk posed by the virus to be low but urged vigilance.

Asked to evaluate US transparency on the outbreak so far, Zhang said the global body had received regular updates and praised a decision to share the virus genetic sequence early.

"I do think the collaboration with US CDC (Centres for Disease Control and Prevention) and the information we've received so far enables us to monitor the situation and to update the preparedness measures," she said.