At least half of Singapore’s newly discovered Covid-19 cases are symptomless, the government has said.
The city-state has increased testing in recent weeks as it attempts to contain its outbreak, having so far recorded more than 38,000 cases – one of the highest infection tallies in Asia.
Authorities have subsequently discovered that “for every symptomatic case you would have at least one asymptomatic case,” according to Lawrence Wong, the minister of national development and co-head of Singapore’s Covid-19 taskforce.
Mr Wong did not reveal the precise number of asymptomatic cases in Singapore, which has reported 6,294 infections in the last two weeks, mainly among migrant workers.
“That is exactly why we have been very cautious in our reopening plans,” he told Reuters.
Mr Wong said that while asymptomatic individuals had fewer opportunities to spread the virus as they were not coughing or sneezing, there have been cases of asymptomatic transmission in Singapore, especially between patients living in close quarters.
“People have commented – why are we not reopening the economy faster?” he said. “We have to take a more cautious approach. There are still asymptomatic cases which we may not have detected circulating in the community.”
Singapore plans to give all its 5.7 million residents a small Bluetooth device, worn on a lanyard or carried in a handbag, to trace interactions with virus carriers.
The first devices could be rolled out to a pilot group by the end of June, Mr Wong said, adding that the government would ensure the confidentiality of any data collected.
Singapore’s findings come as a senior World Health Organisation (WHO) official revealed that it was “very rare” for asymptomatic Covid-19 patients to spread the virus to other people.
Some people who test positive for coronavirus do not develop any symptoms, and are only tested because they have been in contact with someone who has contracted the virus.
Dr Maria Van Kerkhove, head of WHO’s emerging diseases and zoonosis unit, said that although Covid-19 can be spread by patients without symptoms, it is not the main way it is transmitted.
“From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual,” she said.
Last week, Chinese authorities said 300 symptomless Covid-19 carriers in Wuhan, the epicentre of the pandemic, had not been found to be infectious.
But while Dr Kerkhove called the WHO’s own findings positive, she said more research needs to be undertaken if scientists are going to be able to “truly answer” whether the virus spreads easily from asymptomatic patients.
“What we really want to be focused on is following the symptomatic cases,” she added. “If we actually followed all of the symptomatic cases, isolated those cases, followed the contacts and quarantined those contacts, we would drastically reduce [the virus's spread].”
Additional reporting by Reuters
