SINGAPORE - Swabbing stations were set up at a hostel at the National University of Singapore (NUS) on Tuesday (March 23) after traces of Covid-19 were detected in wastewater there.
Residents of 13 units at North Tower in University Town (UTown) were told they have to stay indoors until the results are out.
One of the students, computing undergraduate Chen Xihao, 20, told The Straits Times over the phone: "It never occurred to me that it would happen so close to me."
"They acted swiftly to inform us and took the necessary precautions," he noted, adding that the main inconvenience to him is having to order food in. He also has to attend classes online.
"The general consensus is that it's troublesome, but we understand it's necessary," said Mr Chen.
The affected units have been cordoned off from the rest of the hostel.
In a letter to residents seen by ST, NUS said the authorities had detected low levels of Covid-19 viral ribonucleic acid (RNA) in wastewater samples collected last Saturday between 11am and 5pm.
NUS said the Health Ministry requires all residents in the units to undergo a polymerase chain reaction swab test as a precautionary measure.
These were given in the foyer of the building on Tuesday, and test results will be known in two to three days, said NUS.
The National Environment Agency's (NEA) wastewater surveillance programme is now in about 95 locations, including the four water reclamation plants, workers' dormitories, and other high-population density living premises, such as nursing homes and hostels.
"Monitoring wastewater for Covid-19 is a promising, novel approach for assessing the Covid-19 situation in a community, as infected individuals, including those with mild or no symptoms, could shed the virus in their stool," said NEA in response to queries from ST, adding that wastewater also receives other discharge like mucus, phlegm and sputum.
Meanwhile, students in the 13 units are attending lessons online.
They may leave their hostel rooms briefly for essential activities like using the bathroom, doing laundry and accepting food orders.
They must also declare their temperature twice a day through an NUS online platform and avoid physical contact with others. They also may not have visitors.
Students at the North Tower said that most residents there are international and postgraduate students. Most units have four bedrooms, a shared bathroom and a pantry area, they said.
In the letter, NUS also told students who were in the hostel between midnight last Saturday and 6pm on Monday to return to the hostel immediately to isolate themselves in their rooms.
NUS students were informed last year that their wastewater would be inspected as a precautionary measure for Covid-19.
"I know they have been monitoring, but I never thought they would find anything," said a resident of North Tower, a 26-year-old chemical engineering PhD student who declined to be named.
"At the same time, I think anything can happen during this period."
The university has had a wastewater surveillance programme at all its hostels since Dec 7 last year, as part of efforts to pick up coronavirus cases in a "safe, effective and non-intrusive way", said Dr Peck Thian Guan, director of the university's office of safety, health and environment in another circular.
A complementary tool to clinical testing
Wastewater surveillance allows authorities to detect the presence of Covid-19 in a location, which can then be followed up with clinical tests.
Some 95 locations islandwide currently have their wastewater surveyed including the four water reclamation plants, workers' dormitories, nursing homes and hostels.
The National Environment Agency (NEA) said: "Monitoring is carried out at the water reclamation plants to provide situational awareness of the Covid-19 situation in Singapore, while wastewater sample collection at high-density population... provides an additional surveillance indicator for Covid-19, in addition to clinical testing regimes."
It added that the frequency of sample collection varies from site to site and will depend on the purpose of surveillance.
At NUS, NEA said that it collaborated with the university and provided inputs on the wastewater testing protocol and interpretation of the sample results.
NEA will continue to support NUS in the interpretation of the results as tests are conducted on the samples, said NEA.
Samples from the manholes of interest are collected by autosamplers, programmed to collect them as required.
They are then transferred to the laboratory and processed.
As an example, NEA listed the workers' dormitories where there were reported clusters.
A zero reading for viral material in the wastewater gave added assurance that the dormitories remained free of Covid-19. But if any was detected, swab tests were carried out on workers to facilitate detection and isolation of cases, including asymptomatic ones.
"The passive, wide-area surveillance capability of wastewater sampling therefore enables us to unobtrusively monitor for Covid-19, in conjunction with community clinical tests," said NEA.