What is a super-spreader?

So-called superspreaders are individuals who are capable of infecting a high number of people with certain types of illness. Usually defined as carriers who infect six to eight people, superspreaders are said to have been key to helping previous outbreaks explode internationally. They can be a particular threat if they travel from place to place before they show signs of symptoms or the illness is undetected, as appears to have been the case with Steve Walsh, the British man who infected 11 others during a skiing holiday.

A regular carrier of infections, by contrast, is generally thought to have the potential to infect around two or three people within close proximity, according to Imperial College. Scientists are yet to establish why superspreaders occur in some viruses and not others, but environmental factors, such as close contact in hospitals, can increase the chances of an outbreak exploding.