The Singapore government said on Thursday it had discovered 31 more cases of locally transmitted Zika virus, including a second pregnant woman, taking the total number of cases to 151.

Of the 31, three cases were not linked to any of the previously existing clusters, a joint statement from the Ministry of Health and the National Environment Agency said.

Singapore is the only Asian country with active transmission of the mosquito-borne Zika virus, which poses a particular risk to pregnant women.