Spot the "Super-Spreaders" Among Us

Are you a Typhoid Mary?

Take a look around you. Can you see them? They are moving around us unnoticed all the time, day and night, walking and talking, coughing and sneezing. They touch things like handles, rails, and that $5 bill you just put in your pocket. “Typhoid Mary” was one of their most infamous members. She was responsible for infecting 51 people with Typhoid Fever.
“They” are “super-spreaders” — individuals who spread a disproportionate amount of infectious diseases to the rest of us.
Historically, it was believed that around 20 percent of those infected with a disease such as Typhoid Fever were responsible for 80 percent of the transmissions to others. This has been referred to as the “20-80 rule.”
Now, scientists studying the Ebola epidemic in West Africa during 2014-2015 are discovering that super-spreaders play a more significant role in infectious disease epidemics than was once thought. Findings published this week in the Proceedings of the National Academy of Sciences show that if the super-spreaders had been controlled in this epidemic, two-thirds of the infections could have been avoided.
Mary Mallon, aka Typhoid Mary, was responsible for an outbreak of Typhoid Fever in the early 1900s while she was working as a cook in New York City. Ms. Mallon insisted that she did not feel sick, so she didn’t believe she was making anyone else sick. She continued to believe this, despite the fact that every family she cooked for become sick within about three weeks of her arrival. Mary would simply pick up and move on to another family.
She did this some eight times until she was quarantined for good. Mary spent nearly three decades in confinement before she finally died. Hers was the first medically identified case of asymptomatic Typhoid Fever in the United States.
Scientists are still not sure what causes certain individuals to become super-spreaders. They have posited the possibility of immune system deficiencies in the host as well as the virulence of the virus or bacteria they are spreading. An individual’s potential for super-spreading also includes environmental variables, like proximity to a super-spreader. So whatever the reasons for super-spreaders, they are certainly complex.
So how do we identify the super-spreaders among us? One method epidemiologists use is called “contact tracing” to identify and diagnose individuals who might have come into contact with an infected person. Using this method, super-spreaders have been identified with diseases such as measles, tuberculosis, rubella, monkeypox, smallpox, Ebola hemorrhagic fever and SARS.
Should asymptomatic carriers like Mary Mallon be quarantined for life? In one of the recent SARS outbreaks in Hong Kong, nearly 1,000 spreaders were told to stay home or risk fines and imprisonment if they set foot outside their houses. Will it be necessary to establish modern-day leper-like colonies? Unfortunately, until science provides a way to diminish a spreader’s ability to spread infection, or a way to increase the immunity of those who might be exposed, quarantine seems to be the only option.