Attire for a pandemic. Let’s mask up…

My daughter who studied fashion at Uni. has found a lucrative niche in designer cloth face-masks and they’re proving popular with her fashion-conscious peers and their trendy mothers. My other daughter, teaching overseas, cannot leave her apartment without a surgical face-mask – the blue ones – and off course internationally there is more and more pressure to make the wearing of face-masks in public mandatory. Face-mask fashion is de rigueur, the modern equivalent of the late-medieval Plague Doctor’s attire with a potent nosegay stuffed into his raven’s-beak. What started after SARs in Asia is likely to be a global phenomenon after Covid-19.

The SARS-CoV-2 virus is most likely (we’re still not certain) transmitted by inhalation of both droplets and aerosol near the infected individual. It can also be picked up from infected surfaces such as doorknobs and tables. The virus is microscopic indeed. The virus is as small compared to a party-balloon as a party-balloon is compared to the World; pretty small. And there are lots and lots of them. Each day, a Covid-19 sufferer might emit 10¹¹ viruses; that’s 12 zeros which is a pretty big number. It is also likely that people before they get symptoms if they ever do, are spreading the virus. We are doing what we can to mitigate against this virus; washing our hands often and socially isolating, so what is the evidence of adding the wearing face-masks?

Studies indicate that cloth face-masks, even the most sought after designer ones, are more or less useless in preventing viral transmission, whether worn by the infected or as personal protective equipment (PPE) in those trying to avoid contact.  Surgical face-masks likely have some use in limiting virus dispersal to other people in a healthcare setting by stopping the spread of large cough particles and restrict their dispersion from the infected.

The best measure of a face-masks performance is its filter efficiency and its fit. Masks are supposed to collect viral particles through physical mechanisms.  The gold standard face-mask is an N95 filtering facepiece respirator (FFRs) which is constructed from electret filter material allowing electrostatic attraction of viral particles for additional collection of all particle sizes.

In the US, the National Institute for Occupational Safety and Health (NIOSH) conducted a study of the filtering performance of clothing materials. All cloth face-masks had near zero efficiency at 0.3 µm, a particle size that easily penetrates into the lungs.

Another study evaluated 44 face-masks and unsurprisingly the N95 mask filter efficiency was greater than 95%. Surgical masks exhibited 55% efficiency, general masks 38% and handkerchiefs 2% (one layer) up to 13% (four layers).

Face-mask fit should be a measure of how well the mask prevents leakage of viral particles around the face-mask. The N95 FFRs should fit so that the facepiece lowers the outside concentration of particles by 99%. Cloth masks have very low filter efficiency. Thus, even masks that fit well against the face will not prevent inhalation of small particles by the wearer or emission of small particles from the wearer.

One study suggests that poor fit can be somewhat offset by good filter collection, but will not approach the level of protection required to reduce the risk of viral infection and most cloth and surgical masks have very poor filter performance anyway.

Cloth face-masks in clinical settings go back to the late 1800s, first as infection control on patients and nurses and later as PPE by nurses. Cloth face-masks failed miserably in stopping the 1918 influenza pandemic because the number of cloth layers needed to achieve acceptable particle block made them difficult to breathe through and caused leakage around the mask. So, cloth face-masks are inefficient filters and a poor fit and there is no evidence to support their use by the public or healthcare workers to control the emission of particles from the wearer. Household studies found very limited effectiveness of surgical masks at reducing respiratory illness in other household members and clinical trials in the surgery theatre have found no difference in wound infection rates with and without surgical masks. This is interesting as we all expect our surgeons to keep long-standing practice.

Wearing surgical masks in households appears to have very little impact on transmission of respiratory diseases. One reason may be that masks are not likely to be worn continuously in households suggesting that surgical masks will have no, or very low, impact on disease transmission during a pandemic. A randomized trial comparing the effect of surgical and cloth masks on healthcare worker illness found that those wearing cloth masks were 13 times more likely to experience influenza-like illness than those wearing surgical masks. And we must remember that surgical masks should be single use which is not my experience observing the good people of the Falls Road.

Leaving aside the fact that cloth and surgical masks are ineffective, telling or requiring the public to wear them could be interpreted by some to mean that people are safe to stop washing their hands regularly or isolating at home. Masks will confuse that message and give people a false sense of security.

If masks had been the solution in Asia, shouldn’t they have stopped the pandemic before it spread elsewhere? But I would not want too many people to heed the science as it might disrupt my daughter’s budding fashion business.

“ElvertBarnes.Walk.BaltimoreMD.12April2020” by Elvert Barnes is licensed under CC BY-SA