Man coughing

Spread the word

In infectious disease, not everyone is equal

Just as rumours get spread by a handful of gossip-prone people, the spread of disease can be promoted by some people more than others. Such key individuals are known as ‘superspreaders’.

In SARS (severe acute respiratory syndrome), for example, a Chinese physician spread the infection to several people at a hotel, who then seeded outbreaks in other Far Eastern countries. He infected at least ten people from six countries. And the patient who was responsible for the Canadian outbreak was also a superspreader.

It is not yet known what makes a superspreader – perhaps they just cough more. Possible clues have come from scientists studying the spread of Escherichia coli O157:H7 in cattle, who have found that some 20 per cent of infected animals are responsible for around 80 per cent of transmission. E. coli mainly colonises a particular region of the lower intestinal tract. In the superspreaders the O157:H7 strain seems to dominate this niche.

As they play such an important role in disease transmission, understanding what makes a particular person or animal a superspreader is a key question.

Lead image:

Jess Liotta and Colin Liotta/Flickr CC BY NC


Further reading

About this resource

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

Microbiology, Health, infection and disease, Medicine, Immunology
Education levels:
16–19, Continuing professional development