This water-themed issue celebrates the progress in achieving safer water supplies, as well as the continuing challenges. The 'sanitation revolution' of the last two centuries may have made us complacent about water quality and we ignore the experience of history at our peril, since many of the causes of outbreaks can still readily occur and are part of daily life in water-poor countries. In Jane Austen's early 19th-century England, people accepted that travel, even between two cities, could mean finding that the local drinking waters did not agree with them. Victorians attributed the usually transient episodes of diarrhoea when travelling to a 'change in the waters'. We understand now that this was probably due to lack of immunity to strains of Escherichia coli and other organisms present in the neighbourhood sewage. With no water treatment save for domestic filters to remove contaminants visible to the naked eye, drinking water was often teeming with organisms, including dangerous pathogens such as those causing typhoid fever and cholera. The miasma theory, which held that infections and many other diseases were caused by foul air, prevented most doctors and scientists from recognising the dangers of sewage seeping into water. An exception was Dr John Snow, who researched the possibility that consuming sewage, however dilute and with no visible contamination in the water, was a risk to health. He used his knowledge as a pioneering anaesthetist to propose that the oral route of transmission was most likely to cause diarrhoeal diseases, rather than from inhaling the odorous air of decaying organic matter. A statue of a pump in Soho represents his most famous deductive work, when he demonstrated that the sewage-contaminated water from a street pump caused an outbreak of cholera in 1854. 2 After three years' absence due to building work, the pump statue was restored to Broadwick Street last July (see photo). The action of 'removing the pump handle' by the Parish Guardians, on Snow's advice, is rightly commemorated as a potent symbol of the power of public health intervention. 3 By the late 19th century, the work of microbiologists Robert Koch and Louis Pasteur had brought about a major change in transmission theories, with the germ theory replacing the fears about miasma. Yet, many scientists and physicians continued to claim the effects of evils emanating from soil and the manure and rubbish prevalent in the streets. An outbreak of cholera in 1892 in Hamburg caused over 10,000 deaths: a major cause was mistaken scientific advice, particularly the unsafe water supply to this large port. 4 By contrast, while clusters of cholera still occurred in cities such as London, more reliable sewerage and better water management had reduced the risk of such a wide-scale epidemic. Typhoid fever remained a problem as the carrier state and food contamination were not understood but also since water treatment was only in the early stages, comprising mainly filtration. Chlorination was not established for all UK supplies until the 2...