Epidemiological studies are now revealing that the number of individuals who carry and can pass on the infection, yet remain completely asymptomatic, is larger than originally thought.

But the realisation that asymptomatic people can spread an infection is not completely surprising.

“For any virus or bacteria, making people infectious but not ill is an excellent way to spread and persist in populations,” says Rein Houben, an infectious diseases researcher at the London School of Hygiene and Tropical medicine.

“I warned on 24 January to consider asymptomatic cases as a transmission vehicle for Covid-19, but this was ignored at the time,” says Bill Keevil, professor of environmental healthcare at the University of Southampton.

The first identified case of asymptomatic transmission of Covid-19 occurred in early January, when a traveller from Wuhan passed on the virus to five family members in different parts of the city of Anyang.

One study in the Italian town of Vo reported that 43% of the town’s cases of Covid-19 were asymptomatic, while initial reports from the US Centers for Disease Control and Prevention investigation into the spread of Covid-19 on the Theodore Roosevelt aircraft carrier in March, suggest that as many as 58% of cases were asymptomatic.

Some 48% of the 1,046 cases of Covid-19 on the Charles de Gaulle aircraft carrier proved to be asymptomatic while, of the 712 people who tested positive for Covid-19 on the Diamond Princess cruise ship, 46% had no symptoms.

Houben points out that, because most asymptomatic people have no idea they are infected, they are unlikely to be self-isolating, and studies have shown this has contributed to the rampant spread of the virus in facilities such as homeless shelters and care homes.

Since February, the country that has arguably had the greatest success in suppressing asymptomatic spread of Covid-19 is South Korea.

Armed with a rigorous contact tracing and diagnostic testing regime, which involved dozens of drive-through testing centres across major cities enabling tests to be carried out at a rate of one every 10 minutes, they put specific policies in place to offset the threat of asymptomatic carriers from the moment the virus began to spread out of control in Daegu.

As Korea attempts to prevent a second wave of infections while reopening schools and allowing people to return to offices, preventing asymptomatic spread is one of their main priorities.

It remains to be seen whether the UK government endorses this as an official recommendation, but a recent study across Barts NHS Trust hospitals in London has illustrated how regular testing and social distancing combined with use of facial protection – in this case PPE – can prevent asymptomatic spread of the virus

But if asymptomatic people are not producing a normal antibody response to the virus, what does that mean