Map showing the intimate mixture of the water supply of the Lambeth Company with that of the Southwark and Vauxhall Company, 1854.

Understanding transmission

To halt the spread of a disease, you need to know how it is transmitted

John Snow’s success in stopping a cholera outbreak in London in 1854, by removing the handle of a water pump, is well known. Most people believed that the disease was contracted by breathing foul-smelling air, but Snow was convinced – rightly – that cholera was a water-borne disease.

Hungarian doctor Ignaz Semmelweis (1818–1865) was similarly far-sighted. He realised that doctors going straight from post mortems to delivery rooms were infecting women in labour. By making doctors disinfect their hands, he slashed the incidence of infection.

Sadly, this was before germ theory, and a combination of political factors and, perhaps, Semmelweis’s own stubbornness meant that his ideas were not as widely accepted as they might have been. Thousands of young mothers died unnecessarily as a result.

Today, 150 years after Snow’s death, there is still uncertainty about how certain diseases are spread – for example, how significant badgers are in spreading bovine tuberculosis between cattle.

In one trial carried out in the 1990s, tuberculosis (TB) rates were slightly lower inside badger-culling areas (compared to control areas with no culling), but higher just outside of culling areas. In 2013 new trials in the west of England were carried out to try to establish whether culling badgers could stop the spread of TB, but flaws in the trials made it difficult to come to any firm conclusions.

The devil is very often in the detail. Hospital cleanliness, for example, has been blamed for the rise in hospital-acquired infections such as MRSA (methicillin-resistant Staphylococcus aureus), but the picture is not that simple. The ability to identify and isolate infected patients is more critical – and hard to achieve with the UK’s high rates of bed occupancy.

Lead image:

Map showing the intimate mixture of the water supply of the Lambeth Company with that of the Southwark and Vauxhall Company, 1854. From John Snow, On the Mode of Communication of Cholera. London: John Churchill; 1855.

Wellcome Library, London CC BY

References

Further reading

About this resource

This resource was first published in ‘Epidemics’ in September 2007 and reviewed and updated in January 2015.

Topics:
Microbiology, Health, infection and disease, Immunology, History
Issue:
Epidemics
Education levels:
16–19, Continuing professional development