Researchers carried out the study in response to world leaders and the WHO questioning whether masks were effective.

Wearing surgical masks can significantly reduce the chances of those with COVID-19 infecting others, researchers have claimed.

According to a study by a team in Hong Kong, the rate at which the virus was transmitted through airborne particles or respiratory droplets was lowered by as much as 75% when masks were used.

“The findings implied to the world and the public is that the effectiveness of mask-wearing against the coronavirus pandemic is huge,” leading microbiologist Dr Yuen Kwok-yung, from Hong Kong University, said on Sunday.

Dr Yuen, who helped discover the SARS virus in 2003, said the study was the first of its kind.

He said that his team conducted the study because – while he has long supported wearing masks – world leaders, including the World Health Organisation (WHO), had questioned their effectiveness.

The study saw his team use two cages of hamsters in three different scenarios.

One group was infected with COVID-19 and the other was healthy, with a fan used to push air towards the infected animals – some which did not show symptoms.

Researchers said they found that without any masks between the cages, two-thirds of the healthy hamsters were infected within a week.

But when they placed masks on the cage with infected animals, the infection rate dropped to just over 15%.

The infection rate dropped by about 35% when masks were placed on the healthy hamsters’ cage.

Those hamsters that did become infected were also found to have less of the virus in their bodies than those who were infected without a mask, the research found.

Dr Yuen told a press conference on Sunday: “In our hamster experiment, it shows very clearly that if infected hamsters or humans – especially asymptomatic or symptomatic ones – put on masks, they actually protect other people.

“That’s the strongest result we showed here. Transmission can be reduced by 50% when surgical masks are used, especially when masks are worn by infected individuals.

“Up to this stage, we do not have a safe and effective vaccine.

“What remains practical is still either social-distancing measures or wearing masks.”

The UK government initially said face masks could not protect people, but it has revised its advice and is now recommending people wear face coverings where they cannot remain two metres apart in settings such as small shops and on public transport.

European countries including Italy and Germany have said people should wear masks in such settings.

At the start of the pandemic, which started in China, there was a rush to buy face masks in Hong Kong, where people remember the impact of SARS.

Hong Kong suffered 298 deaths from SARS, second only to mainland China, but the territory has only reported four fatalities from COVID-19.

Walking around without a face mask in Hong Kong, Japan or South Korea is seen as irresponsible, and several US states are also now advising people to wear them when out.