Ridding London of smallpox: the aerial transmission debate and the evolution of a precautionary approach.

The efforts of the Metropolitan Asylums Board in Victorian London to isolate cases of smallpox in hospitals, and so limit its spread, set off a controversy about , i.e. alleged escapes of the disease into the neighbourhood. When, in 1870, the Board began to gather cases of smallpox into its new intra-urban isolation hospitals, nearby householders resisted, and in 1881 their fear of aerial transmission was endorsed by a government medical inspector, W. H. Power. Not all agreed with Power, but as a result from 1885 the Board removed almost all known cases of smallpox in London to hospital ships moored in the Thames Estuary. The ships failed to provide adequate and secure accommodation, however, and so Board smallpox hospitals were erected on the adjacent Dartford marshes. After 1903, there being no more smallpox epidemics in Britain, these isolation hospitals and many similar ones outside other towns and cities were little used for their main intended purpose. Their retention for many years thereafter can be seen as an application of the precautionary principle; it bears on current contingency plans in Britain and elsewhere for dealing with serious epidemics.