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


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