By Claire Mattison
As you probably remember, the Ebola outbreak caused more than 28,000 Ebola cases and 11,000 deaths in West Africa, mainly in Guinea, Liberia, and Sierra Leone. The disease is spread through contact with body fluids of an infected person, while they are symptomatic, and bodies remain infectious even after those infected have died. This made funerals particularly dangerous places for infection.
A new research article that was published last week on the 2014-2016 Ebola outbreak found that up to 61% of cases were caused either directly or indirectly by only 3% of infected individuals. This paper found that the median R0 of Ebola overall was about 2.39 during the epidemic, meaning that one person infected about 2.39 others, but that the actual number varied widely. The study found this by looking at 200 funerals of people who had Ebola and using mathematical models to do contact tracing and find the “index” case for the clusters. These individuals, or “super spreaders,” were major drivers of the epidemic. They have a much larger role than previously described in the Ebola outbreak, and shows the importance of contact tracing and quick identification and isolation of patients with highly infectious diseases.
These super spreaders tended to be under 15 years old or between 40 and 44 years old. They were also more likely to be in the community, as opposed to health care clinics or facilities and spread diseases to many people over a long period of time. People were super spreaders, not just because of the disease, but likely because they were in the community and were being cared for by a large number of other people. As well, it is likely that the older people may have been more important in the community and had more people attend their funerals, resulting in increased spread of the disease. The role of super spreaders within the epidemic also increased in importance over time, showing that are crucial in the continuation of an epidemic.
Super spreaders are not limited to Ebola of course. Typhoid Mary is one really well known super spreader. As well, in both MERS and SARS outbreaks, there were well known super spreaders that infected hundreds of people with the disease. This article and the paper it was based on are interesting because they show how important super spreaders and quick medical care can be to stopping epidemics. In planning and preparation for future epidemics, it will be key to try to identify those who are likely to become super spreaders and to quickly both limit more people from coming into contact with them while also tracing their contacts to prevent further spreading.
News reports on this research article: