Covid-19 patients no longer infectious 11 days after getting sick, research shows

Singapore now discharges patients only after two swab tests are negative for the virus. ST PHOTO: KEVIN LIM

SINGAPORE - After 11 days of getting sick, Covid-19 patients no longer pose a risk of spreading the disease - which means they can be safely discharged.

Singapore now discharges patients only after two swab tests are negative for the virus. But a local study has shown that while the patients might test positive, it "does not equate to infectiousness or viable virus".

That's because the test detects parts of the virus' genome, but is unable to show if they are just fragments of the virus, or if an intact virus is no longer viable and can't infect anyone.

The position paper from Singapore's infectious diseases experts say these new findings allow for revised discharge criteria.

However, the decision on whether to change the discharge criteria has to come from the Ministry of Health (MOH), which was informed of the study results some days ago.

When asked, MOH said: "The Ministry of Health will closely study the position statement and evaluate how we can incorporate the latest evidence on the period of infectivity for persons with Covid-19 into our patient clinical management plan."

It added that Singapore's medical strategy on managing Covid-19 patients is guided by the latest local and international clinical and scientific evidence.

Should MOH accept the evidence from the paper and adopt a time-based discharge, more than 80 per cent of patients could go home after 11 days of illness.

The rest might need longer clinical care because of more severe illness. But they, too, would no longer be infectious after 11 days and no longer require isolation.

The paper was released on Saturday (May 23) by the National Centre for Infectious Diseases (NCID) and the Academy of Medicine's Chapter of Infectious Disease Physicians.

The chapter represents more than a third of Singapore's 87 infectious diseases doctors from both the public and private sectors.

This conclusion in the paper was based on a multi-centre study of 73 patients here.

Professor Leo Yee Sin, executive director of the NCID, said the study is robust and it is safe to generalise to the entire patient population: "Scientifically, I'm very confident that there is enough evidence that the person is no longer infectious after 11 days."

The only exceptions are patients with weakened immune systems, such as cancer patients receiving chemotherapy or people on immune suppressant drugs following a transplant. In them, the virus might remain viable for a longer period.

Dr Asok Kurup, who chairs the chapter in the academy, is equally confident about the results. The infectious diseases expert in private practice said: "Studies are still going on and we will get more data, but we will see the same thing as there is a great deal of science in this. So there is no need to wait."

The paper also refers to a "small but important study" in Germany of nine patients which found viral shedding from the throat and lung to be very high in the first week. But there was no more shedding by day eight.

When asked why it took three days longer in Singapore, Prof Leo said the researchers here were "very conservative and counted till the very last drop".

The researchers plan to publish the results in an international journal of repute.

Join ST's WhatsApp Channel and get the latest news and must-reads.