Non-pharmaceutical interventions, sometimes abbreviated as NPIs, are actions, apart from getting vaccinated and taking medicine, that people and communities can take to help slow the spread of infectious diseases and control epidemics. This week, we are going to look at a range of NPIs that can be used to mitigate the impact of an epidemic of an emerging infectious disease. The objectives of this first part are: to identify the date of the first global pandemic of cholera; to define the incubation period of cholera; to have defined the case fatality risk of untreated cholera; and to discuss the two competing hypotheses about the mode of communication of cholera in the mid 19th century. To start, I want to go back to the foundations of the science of epidemiology, and one of the best-known non-pharmaceutical interventions among infectious disease epidemiologists. This is the story of John Snow, cholera, and the Broad Street pump. John Snow was born in 1813 into a poor family in the North of England. At the age of 14, he was apprenticed to a surgeon, and at the age of 23, he travelled to London, to continue his training. He soon qualified as a surgeon, a general practitioner, and later as a physician. He began to experiment with anesthetics in the mid 1840s, and played a major role in the standardization of the use of anaesthetics, both in terms of the preparation and delivery of the anaesthetic vapors, and in the monitoring of the patient during anaesthesia. He excelled in obstetrics, and became so well known that Queen Victoria invited him to administer anaesthesia to her during the birth of two of her children in the 1850s. Not only was he an accomplished physician, he was also an active scientist, taking time off from his medical practice to study various tropical diseases. Cholera is a diarrheal disease caused by the bacterium Vibrio cholerae. In infected persons, disease appears after an incubation period of 1-3 days. Without appropriate treatment, which is basically rehydration, severe cholera kills about half of affected individuals. While cholera is thought to have been prevalent in the Indian subcontinent for hundreds, or even thousands of years, it did not spread to the rest of the world until the early 19th century. The first global pandemic started in the early 19th century, reaching Europe by the late 1820s. Further pandemics occurred sporadically through the 19th century, killing tens of millions of people worldwide in that century. John Snow first encountered cholera at the age of 18, during his apprenticeship. Cholera returned in a second pandemic in the late 1840s, when Snow was practicing physician in London. At the time, the predominant view of cholera was that it was spread by “miasma”, or “bad air”. An analysis that supported this view was published by William Farr, a famous demographer and statistician. Farr studied the incidence rates of cholera in persons living at different elevations above sea level, and observed that the risk of cholera appeared to be higher in persons living close to sea level, or equivalently closest to the river Thames, where there was more organic matter that produced noxious gases. John Snow took a different view. He was an expert in the behavior of gases, through his work on anaesthetics, and he didn’t think that the miasma theory explained the epidemiology of cholera. In 1849, he proposed an alternative hypothesis, that cholera was a contagious disease acquired through the fecal-oral route, and spread by contaminated water, not through the air. He noted that cholera was a disease of the intestines, not the lungs, pointing to infection via the alimentary canal, rather than the respiratory tract, and he drew an analogy with intestinal worms. Snow noted that cholera thrived in places and subpopulations with poorer hygiene, and suggested that emptying sewage into waterways could contribute to the dissemination of the disease. This was controversial, because proponents of the miasma theory supported the disposal of sewage into the river to reduce the bad smells around cesspits.