Testing for Covid-19 allows for surveillance of groups of people that are at higher risk of contracting or transmitting the disease.

This is in addition to diagnosing patients so they can be cared for appropriately, and facilitating contact tracing to contain the virus' spread.

Health Minister Gan Kim Yong yesterday outlined these three purposes of testing in a virtual press conference by the multi-ministry task force set up to handle the coronavirus outbreak.

Singapore conducts tests for surveillance across hospitals, polyclinics and general practitioner clinics, such as among patients who have already been diagnosed with pneumonia or have prolonged symptoms of an acute respiratory infection.

A random testing programme, known as sentinel surveillance, is also used to pick up cases in the community that may otherwise go undetected. This programme is aimed at finding those who have the virus, but have very mild symptoms or none at all.

Such testing has revealed that there are still cases of Covid-19 being transmitted in the community, with some of these remaining infectious despite their mild symptoms.

Singapore has been expanding its testing capacity, and can now conduct more than 8,000 tests per day, compared with an average of 2,900 tests a day early this month, said the Ministry of Health yesterday.

Mr Gan said targeted testing for selected groups is also in place - for instance, for essential workers who were moved out of dormitories to ensure they are free from infection, as well as for staff of institutions such as nursing homes where there is close contact with seniors.

"We intend to gradually expand testing to a wider pool of essential workers in order to ensure the continuity of critical functions and services. This is also important as we start to open up after the circuit breaker measures."

The authorities have also been widely testing foreign workers for the coronavirus, even those who are well and have no symptoms, following a spike in the number of cases involving such workers in dormitories, who have accounted for the majority of new cases confirmed daily for about two weeks.

They disclosed yesterday that more than 21,000 migrant workers staying in dorms have been tested, with many of them showing no symptoms when they were tested. Close to 3,000 workers have been tested per day.

Mr Gan added that while testing remained a key prong of Singapore's strategy in the fight against Covid-19, "what is more important than testing is for everyone to play our part to prevent transmission by observing circuit breaker rules and guidelines".