Someone who is infected with a particular disease and responsible for transmitting that bacteria or virus to many other people. Epidemiologists say these are often the index cases where an epidemic begins.
Deeper dive
Why someone is a “super spreader,” depends on the kind of pathogen, the infected person’s biology, their environment, and their behavior at the given time. Today, with global travel, the ability to move pathogens rapidly across great distances, often before people are aware they are sick, creates environments ripe for super spreading.
Some infected people might shed more of a virus or bacteria into the environment than others because of how their immune system works. A person who is infected, but with no symptoms, may continue about their daily routines and inadvertently infect more people. A famous example of that type of person is “Typhoid Mary,” a cook who supposedly infected dozens of people with typhoid, even though she wasn’t sick.
Alternatively, people who are sick may be very good at transmitting a pathogen even if they reduce their contacts with others. Individuals who have more symptoms – for example, coughing or sneezing more – can spread the disease to new human hosts. During an outbreak, epidemiologists look for super spreaders, because they can accelerate the rate of new infections in people.