Zika infections were "highly likely" to keep spreading across Asia, the World Health Organisation (WHO) announced on Tuesday.
WHO director Margaret Chan said experts were still looking for ways to deal with the virus, the BBC reported.
"Unfortunately, scientists do not yet have answers to many critical questions," she told an annual regional WHO meeting in the Philippines capital, Manila.
Hundreds of cases of the virus were reported in Singapore while two cases of Zika-linked microcephaly have already been confirmed in Thailand.
Zika generally has mild effects but is more dangerous for pregnant women as it has been linked to severe birth defects, including the brain deformation microcephaly.
According to the WHO, the mosquito-borne virus has been detected in 70 countries worldwide so far.