Science - To mask or not to mask?

By: Ralph Cooney

Reports from the UK and the USA indicate that a low proportion of people (36 per cent in the UK) are wearing masks to counter the spread of Covid-19, despite the disastrous pandemic fatality data in these two countries. This is around 529 deaths per million in the USA and 609 deaths per million in the UK.

In contrast, Asian countries that have had an established cultural preference towards wearing masks (for example, 80 per cent wearing them in China), have had much lower levels of fatalities (three per million). A Belgian study has observed that Asian countries that flattened the curve have generally been the ones that required citizens to wear masks and the European Union countries that did not are now struggling to control the pandemic.

The original reservations about mask wearing in New Zealand were influenced by the need to preserve limited supplies of masks at early stages of the pandemic for clinical workers in the front line of contact. The Ministry of Health is now recommending that everyone who cannot maintain safe distancing of two meters should wear masks. Several countries have now made the wearing of masks mandatory. It seems certain others will now follow.

Covid-19 is embedded and transmitted within a fine spray of mucus droplets formed as a result of coughing, sneezing and even speaking, and is generally not transmitted as a “naked” virus. The virus is small compared to the droplet dimensions – rather like a marble in an inflated balloon. Small mucus droplets carry surface charges that will encourage the droplet to stick to the surface of the mask fibres. Larger droplets also favour the physical trapping of the mucus droplet incorporating the virus.

The surface science of this dual-trapping process has been studied in detail and reported in a peer-reviewed journal paper. This same study has concluded that multiple layers and hybrid materials such as cotton–silk, cotton–chiffon and cotton–flannel produce superior droplet trapping. This scientific information will be useful to any organisations (or individuals) designing and manufacturing masks.  

The extremely contagious nature of Covid-19 reinforces the message about masks. If the virus is present in the community, everyone should wear a mask!


Emeritus Professor Ralph Cooney
r.cooney@auckland.ac.nz

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