The Broad Street cholera outbreak also known as Golden Square outbreak was a severe outbreak of cholera that occurred in 1854 near Broad Street currently known as Broadwick Street. It is in the Soho district of the City of Westminster, London. It happened during the period of 1846–1860 worldwide. This outbreak killed 616 people and is well known as the physician John Snow studied its causes and claimed that contaminated water was the source of this cholera outbreak not the particles in the air. This finding influenced public health and the construction of improved sanitation facilities beginning in the mid-19th century. Later, the term "focus of infection" started to be used to describe sites, such as the Broad Street pump, in which conditions are good for transmission of an infection. Snow's this endeavour also called as double-blind experiment.