William Farr (November 30, 1807 - April 14, 1883) was a nineteenth century British epidemiologist. He was born in Kenley, Shropshire, England to poor parents. He was effectively adopted by a local squire, Joseph Pryce, when Farr and his family moved to Dorrington.
In 1826 he took a job as a dresser in Shrewsbury infirmary. Pryce died in November 1828, and left Farr £500 which allowed him to study medicine in France and Switzerland. He returned to England in 1831 and continued his studies at University College London, qualifying as a doctor with the Apothecaries' Society in March 1832. He married in 1833 and started a medical practice in Fitzroy Square, London. By this time he had become fascinated by medical statistics, a subject which he called "hygology" (derived from "hygiene"). In 1837 he wrote a chapter called "Vital Statistics" for a highly regarded reference book, John MacCulloch's "Statistical Account of the British Empire".
His wife died of tuberculosis in 1838, after which he secured a post in Registrar General's Office as the first compiler of scientific abstracts, on an initial salary of £350 per year. He was responsible for the collection of official medical statistics in England and Wales. His most important contribution was to set up a system for routinely recording the causes of death. For example, for the first time it allowed the mortality rates of different occupations to be compared. In 1839, he joined the Statistical Society and played an active part in it as treasurer, vice-president and president over the years. He remarried in 1842 and had eight children.
There was a major outbreak of cholera in London in 1849 which killed around 15000 people. Early industrialisation had made London the most populous city in the World at the time, and the River Thames was heavily polluted with untreated sewage. Farr subscribed to the conventional theory that cholera was carried by polluted air rather than water - the miasmic theory.
As a result of studying this outbreak, the physician John Snow proposed what is now known to be the actual mechanism for transmission - that people were infected by swallowing something and that it multiplied in the intestines.
There was another epidemic in 1853, and Farr gathered statistical evidence to try to support the miasmic theory. He demonstrated statistically that cholera was spread by polluted water by showing that the likelihood of dying of the disease was linked to the height that the victims lived above the River Thames. He interpreted this as support for the miasmic theory - the air at lower altitudes being dirtier. However he also obtained details of where different water companies drew their water, and generated statistics on the number of deaths per water company. He discovered that people supplied with water from two companies in particular- the Southwark & Vauxhall and the Lambeth water companies - which drew their water directly from the Thames were particularly likely to suffer. Although he did not agree with Snow's waterborne theory, he gave him a great deal of help in collecting data to support it; in particular by providing the addresses of people who had died.
There was a further epidemic in 1866, by which time Snow had died. Farr had by now come around to believe Snow's explanation. He produced a monograph which showed that mortality was extremely high for people who drew their water from the Old Ford Reservoir in East London. By this time, the germ theory of disease had become more widely accepted, partly through the work of Edward Jenner and Louis Pasteur on inoculation; and Farr's work was considered conclusive. The consequence was that public health measures were now directed towards the real cause of cholera. In particular, large engineering projects were started in many cities to collect and treat sewerage, ultimately eliminating the disease in industrialised countries.
Farr served as a commissioner in the 1871 census, retiring from the Registrar General's office in 1879. He received the Gold Medal of the British Medical Association and was made a Companion of the Order of Bath in 1880.