Air-Borne. By Carl Zimmer. Dutton; 496 pages; $32. To be published in Britain by Picador in June; £25
ON MARCH 28TH 2020, as many countries went into lockdown, the World Health Organisation (WHO) posted a tweet: “FACT: #COVID19 is NOT airborne.” People could try to avoid covid by keeping their distance from others and washing their hands regularly. The message was simple. It was also simply wrong: the coronavirus is, in fact, airborne. It can remain active as an aerosol for up to three hours, and the droplets can travel farther than scientists realised. (Consensus-breaking researchers in Guangzhou, China, proved this by studying the transmission of the virus in a restaurant.) Yet it took more than a year—and a huge cache of evidence—for the WHO to change its mind and messaging.
In “Air-Borne”, Carl Zimmer, a science journalist, shows that the WHO’s wrongheadedness has historical precedent. Though epidemiologists have long understood that coughs and sneezes spread diseases, many never took seriously enough the possibility that infective agents could hang around or travel through the air. Instead received wisdom has had it that droplets of liquid, after being exhaled, fall quickly to the ground. Had airborne diseases received due attention from researchers, the book implies, then covid-19 and perhaps some previous influenzas, would have been more quickly controlled or even prevented entirely.
To explain epidemiologists’ resistance to the idea of airborne disease transmission, Mr Zimmer goes back to the early days of germ theory in the 19th century. For decades people believed that “miasmas”—phantasmal toxic vapours—caused disease. (The word “malaria”, for example, is Italian for “bad air”.) But as scientists came to understand more about pathogens, the idea that air could be a source of contagion became deeply unfashionable.
Two of the heroes of Mr Zimmer’s book are William and Mildred Wells, a married pair of American researchers. In the 1940s they conducted experiments to see if ultraviolet lamps could kill germs and purify air, fitting the lamps in hospitals, schools, barracks and even an entire town in upstate New York. The outcome was variable, but with enough successes—particularly against measles—that open minds might have conducted larger, better-funded studies. The second world war, however, put paid to much of their research. It is ironic, Mr Zimmer writes, that America’s biological-weapons programme was predicated on the idea that the pathogens would spread through the air, but that many still refused to change their opinion about how natural germs got around.
Has the message now got through? Engineers have built on the Wells’ research and developed effective “far ultraviolet C” lamps for spaces where aerial transmission of pathogens is likely, such as clubs and restaurants. Yet whether epidemiologists have changed their thinking remains to be seen. The hope is that, when the next pandemic arrives, the WHO and others will give the possibility of airborne transmission more oxygen. ■
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