Not an engineer - a doctor (John Snow), who had experienced an earlier cholera epidemic as a surgeon's apprentice. The "engineer" comes in in another part of the story, the investigation spearheaded by the Reverend Whitehead (mentioned below). But the engineer was incidental, and didn't remove any pumphandles, and didn't initiate anything.
Snow was part of the medical profession, but his ideas don't appear to have been popular at the time - so he did endure the "scorn" of some of his peers, but they were his peers, and he was trained in the same methods as they.
www.ph.ucla.edu/epi/snow/broadstreetpump.html.
<<When a wave of Asiatic cholera first hit England in late 1831, it was thought to be spread by "miasma in the atmosphere." By the time of the Soho outbreak 23 years later, medical knowledge about the disease had barely changed, though one man, Dr John Snow, a surgeon [actually an anesthesiologist] and pioneer of the science of epidemiology, had recently published a report speculating that it was spread by contaminated water -- an idea with which neither the authorities nor the rest of the medical profession had much truck....The year 1853 saw outbreaks in Newcastle and Gateshead as well as in London, where a total of 10,675 people died of the disease. In the 1854 London epidemic the worst-hit areas at first were Southwark and Lambeth. Soho suffered only a few, seemingly isolated, cases in late August. Then, on the night of the 31st, what Dr Snow later called "the most terrible outbreak of cholera which ever occurred in the kingdom" broke out.
It was as violent as it was sudden. During the next three days, 127 people living in or around Broad Street died...Within a week, three-quarters of the residents had fled from their homes... It was like the Great Plague all over again...That it did not rise even higher was thanks only to Dr John Snow.
Snow lived in Frith Street, so his local contacts made him ideally placed to monitor the epidemic which had broken out on his doorstep. His previous researches had convinced him that cholera, which, as he had noted, "always commences with disturbances of the functions of the alimentary canal," was spread by a poison passed from victim to victim through sewage-tainted water; and he had traced a recent outbreak in South London to contaminated water supplied by the Vauxhall Water Company -- a theory that the authorities and the water company itself were, not surprisingly, reluctant to believe. Now he saw his chance to prove his theories once and for all, by linking the Soho outbreak to a single source of polluted water.
>From day one he patrolled the district, interviewing the families of the
victims. His research led him to a pump on the corner of Broad Street
and Cambridge Street, at the epicenter of the epidemic. "I found," he
wrote afterwards, "that nearly all the deaths had taken place within a
short distance of the pump." In fact, in houses much nearer another
pump, there had only been 10 deaths -- and of those, five victims had
always drunk the water from the Broad Street pump, and three were
schoolchildren who had probably drunk from the pump on their way to
school.
Dr Snow took a sample of water from the pump, and, on examining it under a microscope, found that it contained "white, flocculent particles." By 7 September, he was convinced that these were the source of infection, and he took his findings to the Board of Guardians of St James's Parish, in whose parish the pump fell.
Though they were reluctant to believe him, they agreed to remove the pump handle as an experiment. When they did so, the spread of cholera dramatically stopped. [actually the outbreak had already lessened for several days]....
Still no one believed Snow. A report by the Board of Health a few months later dismissed his "suggestions" that "the real cause of whatever was peculiar in the case lay in the general use of one particular well, situate [sic] at Broad Street in the middle of the district, and having (it was imagined) its waters contaminated by the rice-water evacuations of cholera patients. After careful inquiry," the report concluded, "we see no reason to adopt this belief."
So what had caused the cholera outbreak? The Reverend Henry Whitehead, vicar of St Luke's church, Berwick Street, believed that it had been caused by divine intervention, and he undertook his own report on the epidemic in order to prove his point. However, his findings merely confirmed what Snow had claimed, a fact that he was honest enough to own up to. Furthermore, Whitehead helped Snow to isolate a single probable cause of the whole infection: just before the Soho epidemic had occurred, a child living at number 40 Broad Street had been taken ill with cholera symptoms, and its nappies had been steeped in water which was subsequently tipped into a leaking cesspool situated only three feet from the Broad Street well.
Whitehead's findings were published in The Builder a year later, along with a report on living conditions in Soho, undertaken by the magazine itself. They found that no improvements at all had been made during the intervening year. "Even in Broad-street it would appear that little has since been done... In St Anne's-Place, and St Anne's-Court, the open cesspools are still to be seen; in the court, so far as we could learn, no change has been made; so that here, in spite of the late numerous deaths, we have all the materials for a fresh epidemic... In some [houses] the water-butts were in deep cellars, close to the undrained cesspool... The overcrowding appears to increase..." The Builder went on to recommend "the immediate abandonment and clearing away of all cesspools -- not the disguise of them, but their complete removal."
Nothing much was done about it. Soho was to remain a dangerous place for some time to come.
Snow, John (1813-1858), the eldest son of a farmer, was born at York on 15 March 1813. He was educated at a private school in his native city until the age of fourteen, when he was apprenticed to William Hardcastle, a surgeon living at Newcastle-on-Tyne...After serving for a short time as a colliery surgeon and unqualified assistant during the cholera epidemic of 1831-2, he became in October 1836 a student at the Hunterian school of medicine in Great Windmill Street, London. He began to attend the medical practice at the Westminster Hospital in the following October, and in October 1838 he became a licentiate of the Society of Apothecaries, having been admitted a member of the Royal College of Surgeons of England on 2 May 1838. He graduated M.D. of the University of London on 20 Dec. 1844, and in 1850 he was admitted a licentiate of the Royal College of Physicians.