Coronavirus: COVID-19 spread mostly by people showing no symptoms - European scientists

New evidence from scientists in Europe appears to contradict current advice from the Ministry of Health and the World Health Organisation saying COVID-19 can only be spread by people showing symptoms.

The scientists, from Belgium and the Netherlands, analysed data relating to clusters of infections in Singapore and Tianjin in China and concluded that the majority of people who caught the virus there may have become infected from people who had the virus but were yet to show symptoms. 

The findings - which have yet to be peer-reviewed - were published in the infectious disease journal MedRXIV.

The researchers used available data to work out the generation interval of the virus - the time between one person getting infected and them then infecting someone else.

They found that in Singapore the mean generation interval was 5.2 days, while in Tianjin it was 3.95 days.

According to The Guardian, between 45 percent and 85 percent of infections in the Singapore cluster appeared to come from people incubating the virus, while in China that rate ranged between 65 percent and 87 percent. 

The findings are in step with a previous study from Germany, which tracked nine patients and found that by the time people show infections the virus might already be in decline, reports The Guardian.

It also goes against current advice from the World Health Organisation which states on its website that "the risk of catching COVID-19 from someone with no symptoms at all is very low".

The New Zealand Ministry of Health has also focused its containment efforts primarily on people who are showing symptoms.

Earlier this week, Director-General of Health Dr Ashley Bloomfield advised anyone who was even slightly sick to stay away from work.

But as more research emerges shedding light on how the virus spreads, governments around the world may need to update their advice and their methods of fighting the disease.

The researchers concluded that based on their findings, prevention measures such as putting people showing symptoms in self-isolation were not enough to prevent the virus' spread.

"It is unlikely that these measures alone will suffice to control the COVID-19 epidemic. Additional measures, such as social distancing, are required."

In a statement, the NZ Ministry of Health said most reports to date have said that asymptomatic spread is rare.

"They do report that people can spread the infection when in the early stages of the illness (prodromal phase) and that 80 percent of people only have mild symptoms.

"The Ministry acknowledges that epidemiology is constantly evolving and there are many other aspects that also need to be considered."