The Centers for Disease Control and Prevention maintain a list of places where Zika transmission is occurring, which should be consulted before travel, Feist said.
Advertisement
They are not known to have travelled to Zika-affected areas recently, and are thus likely to have been infected in Singapore.
Of the group, 34 people have recovered, while seven remain at a hospital.
A gray alert advises people to pay extra attention to safety issues.
Pregnant women infected with Zika face the additional risk of their unborn babies developing microcephaly, a condition associated with incomplete brain development. Symptoms of the virus include fever, rash, headache, muscle ache and conjunctivitis, although some carriers may not have any symptoms.
Those found with mosquito breeding sites in their homes can be fined up to Sg$5,000 ($3,700).
A total of 118 people working at the construction site have been tested for Zika.
A worker fogs the corridor of a public housing estate in the vicinity where a locally transmitted Zika virus case was discovered, in Singapore August 29, 2016.
Malaysian authorities have enhanced Zika monitoring efforts in preparation for possible locally-transmitted cases of the mosquito-borne disease, after Singapore confirmed its first such case in the weekend.
There are now about 2,500 cases of Zika in the United States, and local mosquito-borne Zika virus transmission has been reported in two areas of Miami, according to the Centers for Disease Control.
The on-site workers quarters at two other dormitories at Senoko South and Kranji were also inspected on August 27.
The Straits Times newspaper quoted local doctor Tan Thai Keng, whose surgery reported four of the latest cases, as saying more women were visiting the clinic as news of the outbreak spread.
On May 13, Singapore reported its first imported Zika virus case and this is the second of the confirmed Zika cases in this year.
Singapore, a densely-populated tropical island with frequent rain, has a chronic problem with dengue, which is spread by the same Aedes mosquito that transmits Zika through bites from an infected person to another human.
Advertisement
Almost all 41 have recovered, but five more suspected cases were yesterday reported by a clinic, local media said.
