Singapore: Singapore urged all pregnant women showing symptoms of fever or rashes to have themselves tested for the Zika virus Wednesday after the number of cases in the city-state soared to 82.

The United States and Britain joined Australia and Taiwan in advising pregnant women to avoid non-essential travel to the city-state.

Environment agency workers stepped up efforts to eradicate mosquitoes that spread the disease, expanding a fumigation campaign centred on the “ground zero” of the outbreak, the eastern suburb of Aljunied.

As infections climbed, they blasted a district of warehouses and industrial buildings at Kallang way to destroy breeding sites that fuelled the outbreak, which began at a construction site housing foreign workers.

Another nearby area - Paya Lebar Way - was also smothered with mosquito-killing chemicals.

Five of the latest infections reported Tuesday were of people who live or work in those two areas.

Zika, which has been detected in 58 countries including hardest-hit Brazil, causes only mild symptoms for most people, such as fever and a rash.

But in pregnant women, it can cause microcephaly, a deformation in which babies are born with abnormally small brains and heads.

The health ministry said that “all pregnant women in Singapore with symptoms of Zika - fever and rash and other symptoms such as red eyes or joint pain” should be tested for infection.

Pregnant women with male partners who have been tested positive were also told to visit their doctors.

“We advise pregnant women to undertake strict precautions against mosquito bites and seek medical attention immediately if they become symptomatic,” the ministry said in a statement late Tuesday.

Sulaiha Ngatiman, 30, who is seven months pregnant with her fifth child, told AFP Wednesday that she was “quite worried” as it was hard to spot Zika’s symptoms.

“I’m going to the doctor tomorrow to get a check up just to make sure I don’t have Zika,” said Sulaiha, who lives in Aljunied.

Construction workers in the affected areas have been given mosquito-repellent patches, chewable Vitamin C tablets and removable sleeves to cover their arms.

Authorities have also deployed “gravitraps” - devices which attract pregnant mosquitos and trap their larvae.

Since Singapore reported its first locally transmitted Zika infection on Saturday, confirmed cases have climbed quickly as authorities ramped up testing, with 82 infections detected by late Tuesday.

Despite being one of Asia’s cleanest cities with high health care standards, Singapore is a densely populated tropical island with heavy rainfall.

It has a chronic problem with dengue fever, which is spread by the same Aedes mosquito that carries the Zika virus. Mosquitoes breed in stagnant water that collects in construction sites, open space and homes.

Singapore’s first reported case of Zika in May involved a man who had visited Sao Paulo in Brazil earlier in the year.

Neighbouring countries such as Malaysia, Indonesia and the Philippines have said they will monitor visitor arrivals from Singapore.