Do surgical masks guard against viral infection?

As I sat waiting for my flight at Los Angeles International Airport, it was hard not to notice the number of prospective passengers wearing surgical masks. A mother and her adult son sat across from me and I watched as the son pulled his mask up above his mouth in order to slurp a pre-flight meal underneath it.

By the time I had returned home to Dublin, the internet was plastered with images of people in airports wearing not only surgical masks but also plastic water jugs over their heads. The new strain of coronavirus has spread rapidly and people seek to protect themselves any way they can. The masks that many are now wearing have their origins in the development of antiseptic surgery in the 19th century and the 1918 influenza pandemic.

There is debate over the efficacy of the masks to prevent the transmission of minute viruses, with some medical professionals arguing that regular hand-washing is much more effective. But there is a sense of comfort in a mask: it feels as though it is filtering the air you breathe in. It was, however, originally designed to filter the air you breath out. The mask was intended to protect the patient from the surgeon rather than the other way around.

Joseph Lister is usually credited with the introduction of antiseptic practices in surgery during the 1860s and 1870s, at least in Britain and Ireland. The discovery of living germs as the causative agents of disease by Louis Pasteur and Robert Koch suggested to Lister and others that these germs might also cause sepsis in wounds.

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Carbolic acid

Lister introduced the washing of hands, instruments and wounds in carbolic acid. By the turn of the century, even further measures to maintain a clean surgical environment were introduced. Among these was the surgical mask (which had in fact been invented many decades before).

If we think of a surgery today, we imagine the staff in scrubs, masks and gloves in a bare, clean room. Yet the scrubs and masks were actually introduced much later than other antiseptic methods. In 1898, an Edinburgh surgeon was only imagining a time in the future when "everyone concerned in an operation . . . shall cover each natural orifice of the body with an antiseptic mask, and clothing themselves in raiment scientifically pure, shall pass into an atmosphere freed from germs". Instead, the surgeon often pounded across permeable wooden floors, his clothes covered with a non-sterilised linen "overall" and was often joined by a number of spectators.

In 1905, the Irish doctor J Rupert Collins performed a series of experiments to prove that exhalations from the mouth (especially when singing or talking) contained bacteria to demonstrate that masks should be worn in the surgery. In 1914, another doctor felt that further demonstrations of the mask's effectiveness were required.

By the time the influenza pandemic began in 1918, however, surgical masks seem to have been in more regular use. And so the idea of using the mask to protect doctors (and nurses and family and friends) from patients grew in popularity.

A great success

Doctors wrote in to the British Medical Journal declaring that the surgical mask was a great success in preventing the spread of the disease. One claimed that a crowded ship of thousands of soldiers kept down the cases of influenza through isolation and the use of masks.

Others cited the experience of using masks in outbreaks of pneumonic plague and other diseases spread by coughing. State public health services promoted the use of masks by those nursing the sick, but soon the wider public also began wearing masks.

Photographs taken during the “Spanish flu” of 1918 to 1920 attest to the popularity of the gauze mask: policemen, typists, commuters, and even baseball players can all be seen wearing masks in an effort to ward off the disease. At the time, health professionals worried that these masks gave the wearers a false sense of security: to be effective they had to be cleaned (or changed) regularly and worn constantly. People rarely met these stringent conditions.

Surgical masks have continued to appear in public every time there is a serious outbreak of a respiratory disease. Diseases like coronavirus cause us to look at the inside of a crowded airport terminal or a bus in the way that pioneering surgeons looked at operating theatres they wanted to keep clean: instead of harmless air they saw a soup of invisible germs.

Dr Juliana Adelman lectures in history at Dublin City University