The isolation of asymptomatic patients may be necessary to control the spread of coronavirus, a new study has suggested.

Scientists say their findings indicate that symptomatic and asymptomatic people have a similar viral load – the amount of virus in an infected person’s blood.

Researchers analysed data from a cohort of 303 symptomatic and asymptomatic patients with Covid-19 between March 6 and March 26, 2020.

Participants were isolated in a community treatment centre in Cheonan, South Korea.

The scientists found that 110 (36.3%) of the participants were asymptomatic at the time of isolation and 21 of these (19.1%) developed symptoms during isolation.

Many individuals with SARS-CoV-2 infection remained asymptomatic for a prolonged period, and viral load was similar to that in symptomatic patient

The cycle threshold values for SARS-CoV-2 in asymptomatic patients – those not displaying any symptoms – were similar to those in symptomatic patients.

The cycle threshold (Ct) during RT-PCR testing refers to when the detection of the virus occurs and helps indicate a person’s viral load – how much virus a person is carrying.

The findings, published in JAMA Internal Medicine, indicate 80.9% of patients with the disease who were asymptomatic at the time of a positive test remained asymptomatic during a median of 24 days from diagnosis.

The Ct values in asymptomatic patients were similar to those in symptomatic patients.

A previous study in a long-term care facility showed 56.5% of patients with the virus were asymptomatic at the time of diagnosis, and 23.1% remained asymptomatic during seven days.

The researchers from Soonchunhyang University Seoul Hospital in Seoul, South Korea, wrote: “In this cohort study of symptomatic and asymptomatic patients with SARS-CoV-2 infection who were isolated in a community treatment centre in Cheonan, ROK, the Ct values in asymptomatic patients were similar to those in symptomatic patients.

“Viral molecular shedding was prolonged.

“Because transmission by asymptomatic patients with SARS-CoV-2 may be a key factor in community spread, population-based surveillance and isolation of asymptomatic patients may be required.”

They added: “Many individuals with SARS-CoV-2 infection remained asymptomatic for a prolonged period and viral load was similar to that in symptomatic patients.

“Therefore, isolation of infected persons should be performed regardless of symptoms.”

The current NHS advice is that people who have symptoms of coronavirus – a high temperature, new continuous cough, or loss of smell or taste – or those who have tested positive for the virus should self-isolate.

This also applies to anyone who lives with someone who falls into those categories or if someone in the support bubble has symptoms or has tested positive.

According to the guidance, those who have symptoms, or live with someone who has symptoms, should be tested.

However, while people at high risk of catching Covid-19 can be tested for the virus even if they have no symptoms, the Government advice is that people should not arrange for testing unless they develop symptoms of Covid-19.