The aristocracy had mostly disappeared from Soho by the 19th century, to be replaced by prostitutes, music halls and small theatres. The population increased significantly, reaching 327 inhabitants per acre by 1851, making the area one of the most densely populated areas of London. Houses became divided into tenements with chronic overcrowding and disease. The 1854 cholera outbreak caused the remaining upper-class families to leave the area. Numerous hospitals were built to cope with the health problem; six were constructed between 1851 and 1874. Businesses catering to household essentials were established at the same time.