IN the 1830s, a new disease began sweeping through Britain which is said to have "shocked society like no other illness had done in recent times and generated everything from general unease to riots".

It was the world's first cholera pandemic, spreading across the globe from India and unleashed thanks to the slum conditions of newly-industrialised cities from Glasgow to London.

Historian Ian Morley, writing in the Yale Journal of Biology and Medicine back in 2007, described how British cities had been transformed into "epidemiological timebombs" with "poorly built houses, a deficiency of ventilation and toilets, unpaved narrow streets, mud, and stomach-turning stenches due to the presence of decaying refuse and sewerage".

HeraldScotland: From the 1770’s to the 1830’s the population of Glasgow soared from 30,000 to over 200,000, causing overcrowding, disorder and unsanitary conditionsFrom the 1770’s to the 1830’s the population of Glasgow soared from 30,000 to over 200,000, causing overcrowding, disorder and unsanitary conditions

No one knew it at the time, but this sewage was the source of the cholera bacteria sickening people via polluted drinking water or the food washed in it; back then the prevailing medical consensus was that disease was spread by "bad air" - the so-called miasma theory.

Edwin Chadwick, a civil servant, was among those who bought into this idea. It is somewhat ironic then that his landmark report in 1842 was to usher in the public health revolution which led to clean water and centralised sewage systems, although his own take was that sanitary reform was required to counteract a threat of insurrection from the "dangerous classes" (that is, the working poor angry about their living conditions) as much as it was an antidote to disease.

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Now, 180 years on, the world finds itself in the grip of another pandemic - this time caused by a virus which originated in China. And, unlike cholera, this disease is airborne.

In May last year, writing the in the journal 'Science', 40 of the world’s leading experts in the transmission of airborne pathogens called for a "paradigm shift" on the scale of Chadwick's Sanitary Report, arguing that Covid underlined for the 21st Century the public health imperative of ensuring that "the air in our buildings is clean with a significantly reduced pathogen count...just as we expect for the water coming out of our taps".

One of the authors, Professor Trish Greenhalgh, added that while personal hygiene like mask-wearing and handwashing was still important "they will be relatively ineffective in the indoor environment until we ensure that the air that we inhale contains far fewer particles that have been exhaled by others in the room".

The current dominant strain, Omicron BA.2, is more transmissible than ever before which means that people need to inhale far fewer aerosol particles to become infected.

HeraldScotland: Probable and definite hospital-onset cases set a new record during the BA.2 Omicron waveProbable and definite hospital-onset cases set a new record during the BA.2 Omicron wave

This is partly why, two years into the pandemic, record numbers of people were catching Covid in hospital during the most recent wave.

Previously the number of 'probable' and 'definite' hospital-onset cases had never exceeded 400 a week in Scotland, but in March it reached 464 and 449 in the weeks ending March 13 and March 20 respectively.

These were patients admitted for other reasons, but who - based on the timing of their positive swab -were almost certainly exposed to the virus in hospital.

READ MORE: Record number of patients caught Covid in hospital during BA.2 wave

Despite all the infection controls and high-grade PPE, roughly 30 per cent of what we call 'Covid admissions' are actually people infected in hospital - patients who require isolation, with all the knock-on effects that has for bed capacity.

The question is, could we - should we - be doing more?

A study by Addenbrooke’s Hospital and Cambridge University, published in November 2021, monitored what happened when Hepa air filter/UV sterilisers were placed in a Covid surge ward.

HeraldScotland: The Addenbrooke's study used AC1500 HEPA14/UV sterilisers manufactured by UK-based Filtrex The Addenbrooke's study used AC1500 HEPA14/UV sterilisers manufactured by UK-based Filtrex

Hepa devices - portable, inexpensive, and easy-to-use - are made up of thousands of fibres knitted together which clean air by filtering out respiratory aerosol particles.

The machines were placed in fixed positions and operated continuously for seven days, filtering the full volume of air in each room between five and ten times per hour.

Air samples showed detectable levels of Covid in the general ward every day in the week before the air filters were switched on, but none on any of the five days after they were activated. Sampling also showed reduced levels of bacterial, fungal and other viral bioaerosols.

Yet, even in schools, official advice remains that Hepa filters be used only in "exceptional" cases.

Meanwhile, research published in March showed exciting potential for a new type of ultraviolet light to make indoor environments safer.

Scientists - including experts from Dundee and St Andrews - tested far-UVC lamps installed in the ceiling of a chamber into which an aerosol mist of Staphlococcus aureus was continuously sprayed.

The microbe was chosen because it is slightly less sensitive to far-UVC light than coronaviruses, suggesting that the results might be even stronger for the best known of that viral family: Covid.

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UVC light has long been know for its ability to kill bacteria and viruses, but is also potentially hazardous to human skin and eyes.

Far-UVC, by contrast, has a shorter wavelength and appears harmless to human cells.

The team found that the lamps took less than five minutes to destroy 98 per cent of the airborne S. aureus microbes - equivalent to the disinfecting power of 184 equivalent air exchanges per hour (a typical operating theatre will have around 20 air changes per hour).

HeraldScotland: The Old Course, St Andrews. Far-UVC lamps were said to have the potential to make indoor settings as safe from airborne pathogens as the famous golf course 'on a windy day'The Old Course, St Andrews. Far-UVC lamps were said to have the potential to make indoor settings as safe from airborne pathogens as the famous golf course 'on a windy day'

Dr Kenneth Wood, a physics lecturer and senior author of the study, said the results were "spectacular" and "far [exceeded] what is possible with ventilation alone", adding: “In terms of preventing airborne disease transmission, far-UVC lights could make indoor places as safe as being outside on the golf course on a breezy day at St Andrews.”

It's early days, but if water sanitation put an end to cholera outbreaks in Britain, perhaps the long-term effect of the current pandemic will be cleaner indoor air and substantial reductions everything from influenza to Covid.