In the 1840s, a prominent health notion of the time – the “miasma theory” – suggested that bad smells and bad air led to people contracting diseases such as cholera and the Black Death. By the end of the decade, more than 50,000 deaths had been recorded in England and Wales.
In 1849 John Snow – a young physician considered one of the founders of modern epidemiology – had become sceptical of the prevailing theory and suggested that contaminated water may instead be the main form of transmission.
