New research conducted on hamsters by Hong Kong scientists offers proof that wearing surgical masks can significantly reduce the rate of airborne COVID-19 transmission.
The study, hailed as the first of its kind by the team, discovered the rate of non-contact transmission - infection via respiratory droplets or airborne particles - decreased by as much as 75 percent when masks were involved.
Almost 5 million people worldwide have contracted the novel strain of coronavirus, SARS-CoV-2, which causes the COVID-19 disease. More than 315,000 people have died due to the virus, which can be particularly harmful to those with underlying health conditions.
"The findings implied to the world and the public that the effectiveness of mask-wearing against the coronavirus pandemic is huge," Dr Yuen Kwok-yung of Hong Kong University said on Sunday (local time), as reported by the South China Morning Post (SCMP).
However, the leading microbiologist reiterated that contracting the virus is still possible, even while wearing a surgical mask.
Whether or not to wear a mask has become a hot topic throughout the pandemic, with health experts sitting on both sides of the argument. While many countries have made wearing a mask mandatory in public, other authorities - such as New Zealand's Ministry of Health - have challenged its effectiveness. Director-General of Health Dr Ashley Bloomfield has cited the frequent need for readjustments and associated face-touching as reasons why masks are not a necessity in the fight against COVID, saying many cheap and ill-fitting coverings do little to prevent transmission. Even the World Health Organization (WHO) has challenged the necessity of masks.
Dr Yuen - a mask advocate - said the study was largely undertaken in response to the sharp pro-mask, anti-mask divide among leading health authorities.
In their experiment, partitions made of surgical masks were set up between cages in an isolated facility, with an infected hamster on one side and three healthy hamsters on the other. A fan was then placed in between to ensure the virus would "transmit" between the cages, the SCMP reports.
Fifty-two hamsters were used in the tests, which were carried out under three scenarios designed to replicate real-life situations. The first scenario had mask barriers placed only on cages that held infected subjects; the second had partitions placed only on the uninfected side; and the third had no partition at all.
After seven days, 66.7 percent, or 10 out of 15 healthy hamsters placed in cages with no partition, had become infected.
But when surgical mask barriers were placed on the infected hamsters' side, only two of 12 subjects in the adjoining cage - or 16.7 percent - tested positive for COVID-19.
When the partition was placed only on the cage with healthy subjects, that number rose to four out of 12.
Dr Yuen said the experiment effectively demonstrates that when infected hamsters - or humans - don masks, it can protect others from contracting the virus.
"That’s the strongest result we showed here," he said.
"Transmission can be reduced by 50 [percentage points] when surgical masks are used, especially when masks are worn by infected individuals."
The study also found that hamsters infected with COVID-19 via a direct injection had more severe symptoms than the hamsters which became ill through the mask partitions. The latter group experienced milder histopathological changes and lower viral loads in respiratory tract tissues, the SCMP reports.
Dr Yuen said that while there is no vaccine for SARS-CoV-2, wearing masks and social distancing measures are the only practical solutions to avoiding infection.
He advises those who are reluctant to wear a mask to consider donning one when in an indoor or closed environment where there is no free air exchange, in crowded places or on public transport.
Yuen and his team of researchers previously established the world's first golden Syrian hamster model for COVID-19 in February, showing hamsters - which have enzyme receptors much like those in humans - could transmit the virus from one to another through direct or indirect contact.
The Ministry of Health has been staunch in its stance on masks, saying New Zealanders are welcome to wear one if it makes them feel more comfortable. However, Dr Bloomfield has reiterated there isn't enough evidence to suggest that masks are truly effective at preventing transmission - hence the ministry has not made an official recommendation to wear masks in public places.
"For most people in the community, PPE such as face masks are not recommended. However, for people with symptoms of an acute respiratory infection, the World Health Organization recommends that there may be benefit in wearing a face mask to reduce the spread of infection to other people," says the ministry's website.
During Tuesday's daily COVID-19 media briefing, Dr Bloomfield was asked whether he and the ministry had revised their position on masks, particularly as public transport resumes its usual schedule under alert level 2.
"Not at this point, but it's still very actively under consideration. Not just whether masks may be useful on public transport, but all the different policy implications, including around supply for people; whether use of masks on public transport may mean relaxing some of the physical distancing arrangements; whether it's just public transport or in other settings," he explained.
"Also the relevance of using them in alert level 2 and especially if we're looking to move to alert level 1."
Dr Bloomfield claimed the ministry is not "reluctant" to recommend the use of masks, but reiterated the importance of policy implications and considerations, including the public's access to the product.
"What is an increasingly very low risk of there being community transmission out there definitely influences whether or not we should be advising or recommending the use of masks," he said.
The Ministry of Health has been contacted for its opinion on the findings.