A fascinating book that looks at the history of air-borne diseases, from the people who investigated the possibility that some diseases might be air-borne, to the current day COVID-19 outbreak, which many (including the WHO) initially declared was not an air-borne disease, until the weight of evidence and studies eventually forced authorities to accept that it was air-borne. Hopefully, the lessons to be learned from COVID-19 may be used to blunt the effects of the next air-borne pandemic.
The book starts with the history of diseases, between those who believe diseases were spread by contagion (close contact) and by miasmas ('bad air'). The germ theory of diseases would help settle the matter on the side of contagion. But those who studied the air would find that it was filled with particles (spores, fungi and germs), even high in the stratosphere. While there was evidence that some diseases, like plant rust, could be spread by air, most researches dismiss it, believing that disease causing particles were mainly spread by close contact. As most, some diseases may be spread by droplets (via coughs and sneezes) but the droplets were considered too heavy to be kept air-borne for long.
But some scientists did believe that some diseases, like influenza, tuberculosis or measles, could be air-borne. They ran experiments, using ultraviolet lights to sterilise the air, and equipment to capture air-borne diseases particles, to gather evidence. But such experiments are hard to run and to reproduce properly. It also didn't help that one of the principle scientists advocating for air-borne diseases featured in the book, William Firth Wells, was considered hard to work with and was his own worst enemy at advocating for air-borne diseases.
During the world wars, research into air-borne diseases would turn from prevention to causing diseases, especially in enemy areas. Bioweapons were developed (like rust or anthrax) but never deployed at large scale as the effects were either not great enough or not specific enough (diseases don't discriminate over who gets infected). But accidents do occur, showing the effects bioweapons could have on populations if they were ever used.
Eventually, major health organisations, like the US CDC (Centre for Disease Control) would dismiss most of the work on air-borne diseases. One unfortunate 'fact' that would emerge from this episode was the belief that only particles smaller than 5 microns can be air-borne. This was a mis-statement, as only such tiny particles can penetrate deep into the lungs to cause diseases like tuberculosis: larger particles could still be air-borne and cause diseases if they do not have to penetrate as deeply (like COVID-19).
Moving to the modern era, the book looks at some pandemics and incidents (like bird flu, Ebola, AIDS, anthrax attacks) that would cause panics over whether they could become air-borne diseases. These would divert attention and resources from the few known air-borne diseases, preventing research into methods to make the air safer (like providing proper ventilation and filtration).
Then, COVID-19 appears, causing a global pandemic. While vaccines would eventually help end it, the death toll might have been lower if COVID-19 had been recognised as an air-borne disease earlier, leading to better prevention methods like better ventilation, instead of promoting less effective methods like social distancing or constant handwashing.
Today, there is now more research into air-borne diseases and to particles in the air in general. Fast DNA sequencing and other methods have now shown that air-borne particles can travel high in the air and for thousands of miles. Better ventilation and methods to sterilise and filter the air are being advocated for better health.
Hopefully, we are now better prepared when the next air-borne pandemic appears.
