The World Health Organization has said that a disease linked to the Zika virus in Latin America poses a global public health emergency requiring a united response.
With the increasing report of infection as a result of the virus, experts are worried that it is spreading far and fast, with devastating consequences.
The infection has been linked to cases of microcephaly, in which babies are born with underdeveloped brains.
The WHO alert puts Zika in the same category of concern as Ebola that ravaged some countries in Africa.
It means research and aid will be fast-tracked to tackle the infection.
There have been around 4,000 reported cases of microcephaly in Brazil alone since October, the BBC reported.
WHO director general, Margaret Chan, called Zika an “extraordinary event” that needed a co-ordinated response.
“I am now declaring that the recent cluster of microcephaly and other neurological abnormalities reported in Latin America following a similar cluster in French Polynesia in 2014 constitutes a public health emergency of international concern.”
Dr Chan justified declaring an emergency even amid uncertainties about the disease, saying it was time to take action.
The WHO faced heavy criticism for waiting too long to declare the Ebola outbreak a public emergency.
Currently, there is no vaccine or medication to stop Zika. The only way to avoid catching it is to avoid getting bitten by the Aedes mosquitoes that transmit the infection.
The WHO has already warned that Zika is likely to “spread explosively” across nearly all of the Americas. More than 20 countries, including Brazil, are reporting cases.
Most infections are mild and cause few or no symptoms, although there have been some reported cases of a rare paralysis disorder called Guillain-Barre syndrome.