Rome ? The bird flu virus that has hit several Asian countries is likely to spread to Europe, the Middle East and Africa, the United Nations Food and Agriculture Organization warned Wednesday, urging nations at risk to step up surveillance and prepare national emergency plans.

The most immediate threat is to poultry farms, but the virus’ spread also increases fears that it could mutate into a form dangerous to humans.

Eliminating the bird flu outbreak is important for human health because each time the virus passes from bird to bird, it has the opportunity to mutate into a form that is deadly to humans and easily spread between people. That could trigger a pandemic that could claim the lives of millions of people across the globe.

Experts have warned the risk is high of a human flu pandemic, and control efforts are focused on ensuring the current bird flu strain does not trigger that.

Wild water birds flying from Siberia, where the virus has recently spread, may carry the disease to the Caspian and Black Seas “in the foreseeable future,” the Rome-based FAO said.

“These regions … could become a potential gateway to central Europe for the virus,” the agency said in a statement.

Bird migration routes also run across Azerbaijan, Iran, Iraq, Georgia, Ukraine and some Mediterranean countries, so bird flu outbreaks in these areas also were possible, the agency said.