The challenge
In rapidly growing nineteenth-century cities, people drank from wells, rivers and pumps that were often close to cesspools, graveyards and open drains. Diseases such as cholera and typhoid killed many, and the causes were disputed. A widely held view, miasma theory, held that foul air from rotting matter caused illness. The challenge was to figure out how disease actually spread, and then to build systems, such as drains, sewers, filters and treatment plants, that kept waste out of drinking water. This needed good evidence, political will, large sums of money and ongoing maintenance. It also needed ordinary people to change habits, from how they disposed of waste to how they washed their hands.
The people
John Snow, an English physician, argued that cholera spread through contaminated water. In 1854 he examined an outbreak around Broad Street in London and recommended removing the handle of a local pump. The Reverend Henry Whitehead, a local curate with detailed knowledge of the neighbourhood, traced the outbreak to a baby who had died on 2 September and carried out his own inquiry, which complemented Snow's. Joseph Bazalgette, chief engineer to London's Metropolitan Board of Works, designed the capital's main sewer system. Later, engineers and public-health officials in many countries developed filtration and disinfection. Today, the WHO/UNICEF Joint Monitoring Programme tracks progress worldwide. Behind all of these names were builders, inspectors, local officials and communities who dug trenches, laid pipes and ran treatment works.
The contribution
Snow's analysis connected cases to a water source and challenged the dominant theory. UCLA's historical summary of the outbreak notes that he presented his case to the parish Board of Guardians on 7 September 1854 and that the pump handle was removed soon afterwards. After the hot summer of 1858, known as the Great Stink, Parliament funded Bazalgette's scheme; the Museum of London records about 1,100 miles of drains feeding 82 miles of brick-lined main sewers, built with some 318 million bricks and opened in 1865, with the project finished in 1875. In the United States, the Centers for Disease Control and Prevention reports that Jersey City began routine disinfection of its community drinking water in 1908 and that thousands of other towns followed; typhoid fell from about 100 cases per 100,000 people in 1900 to 33.8 by 1920.
The wider context
Public-health reform sat alongside the growth of germ theory, statistics and municipal government. Many places built waterworks and sewers in the nineteenth and early twentieth centuries, often after outbreaks or political scandals, and many traditions of water management existed before them, from aqueducts and wells to household filtration in different regions. Reforms also reflected inequality: wealthier districts often received services first, and colonial cities were frequently served unevenly. After World War II, international agencies and national governments extended water and sanitation programmes to more places, and the United Nations later adopted Sustainable Development Goal 6, which calls for safe water and sanitation for all by 2030. Today's global picture is tracked by the WHO/UNICEF Joint Monitoring Programme.
Obstacles along the way
Snow's case was not universally accepted at the time. The 1854 UCLA account notes that officials were sceptical and that a family physician disputed the cholera diagnosis of the first case; a committee vote in 1855 on whether pump water was responsible was split and decided by the chairman. Most of the medical establishment favoured miasma theory. London's sewers were driven largely by the smell crisis, and they carried waste downstream instead of treating it. Disinfection's contribution to disease decline is difficult to separate from other factors; CDC credits it together with better source water, treatment and sanitation. The biggest obstacle today is uneven access. WHO and UNICEF report that, in 2024, 2.1 billion people lacked safely managed drinking water, 3.4 billion lacked safely managed sanitation, and 354 million practised open defecation. Fragile and low-income settings face the largest gaps.
Why it matters
Safe water and sanitation are among the most effective health interventions, protecting children and communities from diarrhoeal disease and supporting schools, work and dignity. The 2025 JMP report found that rural drinking-water coverage rose from 50 to 60 percent between 2015 and 2024, while urban coverage stagnated, and warned that universal safely managed coverage by 2030 appears increasingly out of reach. This story therefore combines a historic success with an unfinished task. It also shows how evidence, such as maps and interviews, can overturn entrenched beliefs, and how infrastructure is a form of collective care that depends on public funding, maintenance and trust. These are educational facts, not medical advice; local health authorities can advise on water safety where you live.
What we can learn
Trace the chain of evidence. Snow's map persuaded people not because it was beautiful but because it connected cases to a cause. Notice the difference between a theory, such as miasma, that feels intuitive and one that survives testing. Watch for the gap between invention and delivery: a technology that exists in one city is not the same as access for everyone. Check dates when you read statistics, since the figures quoted here are from the 2025 JMP report with data to 2024 and will be updated. Finally, look around you: who builds and maintains the pipes, treatment works and drains you rely on, and what would happen if their work stopped?
