The World Health Organization setting up what it calls a global response unit amid concern about the spread of the Zika virus.

FOX's Simon Owen reports from the European bureau:

Doctor Anthony Costello at the World Health Organization saying most people who contract Zika won't get sick:

(Costello) "But the problem is that the complications of this relatively mild illness do have potentially devastating effects for families."

The virus suspected in a wave of birth defects in Brazil. Officials say four million people across the Americas could catch Zika this year.

Costello saying the first priority is urging women in affected areas:

(Costello) "To take every possible measure for personal protection against being bitten by mosquitoes."

He warns a vaccine is likely years away.

In London, Simon Owen, FOX News.