Unmasking the Unexpected Success
“Personally, I would hope we as scientists at least could explain the complexity behind the varying scientific evidence, and despite the seemingly contradictory results how we eventually come to the conclusion that we believe masks, although not perfect, would still reduce transmission at least in some extent.”
During COVID-19, one of the most contentious issues has been the efficacy of a mask for public health protection. Asia has found a widespread acceptance of masking for community health protection. However, the same could not be said across Europe and North America.
In early April, findings from the study “Respiratory virus shedding in exhaled breath and efficacy of face masks” published in Nature Medicine, suggests that surgical masks can be effective in preventing transmission from symptomatic people.
Since publication, the study has been one of the most highly cited articles on the efficacy of face masks in preventing transmission of viruses.
We spoke to the lead author of the study Dr. Nancy Leung Hiu-lan, Research Assistant Professor of School of Public Health, to discuss her study and the sudden success of her study.
Congratulations on your study “Respiratory virus shedding in exhaled breath and efficacy of face masks” becoming one of the most highly cited studies in 2020.
Thank you. It was a pleasant surprise. Although I believed in the scientific value of the study, if it were not for COVID-19, the study would not have garnered such international attention.
What was the inspiration for the study?
When Professor Cowling and I first designed the study, I was interested in understanding the potential difference in transmission mechanisms between different respiratory viruses regardless of their public health importance; although the study would also inform the effectiveness of mask on reducing transmission, which now has shown to have important public health implications.
How do you feel about the attention the study is getting?
I am humbled by the attention, as many scientists before me had done the hard work for the accumulation of technology and knowledge to allow the present study possible. I sincerely hope that these scientists and studies would also get the attention they deserve.
Knowing what you knew from your own study, what was your thought on the mask vs no mask debate that was happening globally?
From a scientific point of view, I understand why there is a debate.
Indeed, there are varying evidence in the scientific literature that either successfully or unsuccessfully demonstrates that masks are effective. This can depend on the design of the study and how we define effectiveness.
For example, we can define the effectiveness of masks as a source control when worn by an infected person, or as for protection against infections when worn by a healthy individual; or in terms of reducing the release of respiratory viruses from the exhaled breath of an infected person, or reducing transmission between individuals.
On the other hand, as with other public health issues, the mask vs. no mask debate is not only a pure scientific consideration of effectiveness but also involves resource availability, priority of resource allocation, acceptability due to cultural differences, personal freedom, civic responsibility to the society as a whole, and may even be politically polarised in some countries.
What role do you think scientists play in communicating with the public?
Personally, I would hope we as scientists at least could explain the complexity behind the varying scientific evidence, and despite the seemingly contradictory results how we eventually come to the conclusion that we believe masks, although not perfect, would still reduce transmission at least in some extent.
The study was a long arduous 3-year study, can you tell me more about the process? How did you find participants?
It actually took around 8 years from start to finish.
Wait, the study took 8 years?
Yes. We spent about 2 years during the planning stage.
We needed to secure the initial research funding, get the huge machine shipped from our collaborators in the US to Hong Kong, and to secure a site in a local hospital (Hong Kong Baptist Hospital) that had a negative pressure room in the outpatient clinic for us to put the machine. It was essential for us to recruit individuals with respiratory illness and have them participate in our study immediately while still being ill.
Then the participant enrolment spanned about 4 years.
We also spent around 2 years to develop the laboratory assays needed to identify these diverse groups of respiratory viruses, data cleaning, and statistical analyses.
That is a long time to commit to a study. How did you find participants for the study?
We stationed in the outpatient clinic and asked patients with respiratory illnesses some screening questions to assess their eligibility.
It took so long to collect enough samples for each respiratory virus, as respiratory illness could be caused by different respiratory viruses and these viruses may circulate in different parts of the year.
For example, we only identified 54 individuals with rhinovirus infection out of over 3300 individuals screened from across 4 years, although it was already the most commonly identified infection in the study.
8 years is a really long time. Knowing what you know now, what would you tell Nancy Leung in 2015 while working on this study?
I would tell the 2015 me or remind the future me that, generating new scientific knowledge is my first and foremost responsibility as a scientist and should always come first regardless of the circumstances. Every small step counts.
This machine you used for your study; can you tell me more about it?
The exhaled breath collecting device, the Gesundheit II (G-II), is an invention of Dr. James McDevitt, Prof Donald Milton, (my Ph.D. co-supervisor), and colleagues at the Harvard School of Public Health and the University of Maryland in the United States.
There are only 3 or 4 G-II machines in the world and they are all being used for research purposes.
The uniqueness of the G-II lies in its ability to recover live respiratory viruses from fine aerosols, which is one of the key pieces of evidence required to demonstrate the potential of aerosol transmission.
It works by sucking all the exhaled breath from an individual into the machine using a strong continuous airstream, while the individual is sitting inside a closed tent with his/her head placed inside the G-II.
The machine then separates the exhaled breath into either large droplets or fine aerosols and then collects them into separate samples into a culture medium.
The machine looks frightening?
It was actually quite challenging to set up and operate, the G-II was big and required some physical strength for both disinfection and putting the parts together.
Were participants intimidated?
Some participants were intimidated by the sheer size and the many complicated-looking meters and other parts of the G-II.
We needed to emphasise to participants they can stop the collection at any time.
How did you feel about the debate on aerosol transmission?
To be honest, I am not surprised at all that aerosols could be a potential mode of transmission for coronaviruses.
Based on previous studies from our team as well as other scientists in the field working on aerosol transmission, it’s been demonstrated it could be the case for many respiratory viruses such as influenza.
The important question now is how the potential for aerosol transmission may affect the transmissibility of a respiratory virus.
Any funny stories during your study?
Oh yes, one funny story happened during the planning stage. We attempted to place a warm mist humidifier in Hong Kong to maintain a high humidity inside the tent for optimal operation as was needed for a similar study in the US. Humidifiers are commonly found in the US.
After many attempts to identify one, we realised we were more likely to find a dehumidifier than a humidifier.
Actually, we might not need a humidifier to maintain the humidity inside the tent in the first place during the Hong Kong summers.
Anything else about your study you’d like to say?
Ah yes, a very sincere gratitude to my colleagues at the HKU School of Public Health who shared the occasional back pain.
And, a heartfelt thanks to all the participants of the study for enduring while staring inside the G-II without doing anything else during the entire 30 minutes of exhaled breath collection.
You currently have another study you are working on?
Yes, I am currently conducting a series of community-based longitudinal observational cohort studies and vaccine trials to this end, to understand what is the difference in the immunity between different individuals to explain why some people would have more severe disease than others during infection by the same respiratory virus.
Thank you for your time and we look forward to your next research study.
Thank you for having me.
