Steve Walsh, a 53-year-old Briton, has a new nickname that sounds like a Marvel hero. Not a nice character, rather a very bad guy. In recent days, the Anglo-Saxon press has baptized this ordinary businessman “super-spreader”. Either, in French, super-contaminator, or super-propagator. This 50-something native of Hove, in the south of England, who unintentionally infected ten people with the new Covid-19 coronavirus after a business seminar in Singapore, now has his photo on all newsstands in his country.
It must be said that it is the cause of five of the eight positive cases counted in the United Kingdom. This father, now recovered, also infected six other Britons, including a 9-year-old child, during his vacation, this time in France, in the Alps ski resort with the predestined name: Les Contamines-Montjoie .
Health authorities from Paris to London are now carrying out a large investigation to find out if other people may have been infected. So far, nothing to report. But what is so special about Steve Walsh? We take stock of what we know about super-spreaders.
What is a super-spreader?
An individual with a contagious virus can infect a number of people. “In the case of the new coronavirus, the average is between two and three people,” says Olivier Terrier, a CNRS researcher at the International Center for Research in Infectious Disease. A super-spreader infects many more people than the average person. This is the case of Steve Walsh, who infected at least eleven individuals.
The term super-spreader is specific to epidemiological jargon. “Used in this way in the media, it can seem very anxiety-provoking when it does not necessarily represent dangerousness,” specifies the researcher.
How long has this term been used?
Popularized with the Sras epidemic almost twenty years ago, the first documented case dates back to the beginning of the 20th century. Mary Mallon, an Irish cook who emigrated to the United States and a healthy carrier of typhoid, had infected around fifty people. Arrested, then released, then arrested again, she remained locked in a hospital, to avoid any contamination, until her death in 1938. The press had nicknamed her “Typhoid Mary”.
After the emergence of SARS in 2002, “several episodes of super-spreading have marked the epidemic,” recalls Arnaud Fontanet, head of the epidemiology unit for emerging diseases at the Pasteur Institute. And to cite the striking example of Amoy Gardens: more than 300 people had been infected by the coronavirus in this residential subdivision in Hong Kong. Forty of them had not survived. The disease was imported by a Chinese man who came to visit his brother. The investigation later demonstrated that the virus was circulating through the pipes in the bathrooms.
Why does an individual become a super-spreader?
Not a super-spreader who wants to. “It could be linked to the person himself: his physiognomy, the fact that he secretes more viruses than the average, or that he is contagious before he even experiences symptoms,” explains Olivier Terrier. It is also linked to the environment, to his behavior: someone who travels a lot, who is in contact with many people, such as nursing staff, who stays in a confined space… ”lists the researcher.
Still many mysteries surround this phenomenon, “which has never really been documented,” says Arnaud Fontanet of the Institut Pasteur. “We have not been able to demonstrate that these people secrete more viruses. We still do not understand precisely what happens during these episodes of super-spreading. “
What is their role in an epidemic?
A super-spreader helps create a new cluster – a grouping of several cases around an initial case – and can become the starting point for a secondary epidemic. “The authorities must be vigilant so that an epidemic does not restart in another corner of the globe,” explains Olivier Terrier of the CNRS.
It is therefore essential to identify super-spreaders, “in order to understand the transmission process and better prevent epidemics”. “The quality of the information reported during these episodes outside of China allows us to move forward and analyze the situation,” adds Arnaud Fontanet.
How many Covid-19 super spreaders are there?
For the moment, only Steve Walsh has been entitled to such publicity. “For now, it’s just a spark and our goal remains to contain it. We really need to join forces to fight this virus before the situation gets out of hand, “said Tedros Adhanom Ghebreyesus, director general of the World Health Organization, on Monday.
WHO executive director Michael Ryan nevertheless rejected the idea of an episode of massive super-spreading, calling on the media not to personalize the disease.