COVID-19 and the Super Spreader
The following is an excerpt from a conversation with Dr. Ben Cowling, an NIH-funded epidemiologist at the University of Hong Kong.
Clustering and superspreading potential of SARS-CoV-2 infections in Hong Kong.Adam DC, Wu P, Wong JY, Lau EHY, Tsang TK, Cauchemez S, Leung GM, Cowling BJ .Nat Med. 2020 Nov;26(11):1714-1719. doi: 10.1038/s41591-020-1092-0. Epub 2020 Sep 17. PMID:32943787.
Q, What is a "super spreader"? How is it advancing the COVID-19 pandemic?
A.We investigated the infections in Hong Kong and what we discovered is that the infections occurred in clusters. On average, one person could be infecting another two people, but in practice, this is not the case in many cases.
From the cases, we found that 70% of the patients did not infect or affect anyone else. And we found that about 20% of the patients in the cases were responsible for 80% of the infections. Those cases are called "super spreaders".
Q, Has this pattern been observed before? Is this a story limited to Hong Kong?
A.A small number of cases have been found to be involved in the majority of infections. And this is not the first time this has happened, it happened in 2003 with SARS (another coronavirus) and MERS (Middle East Respiratory Syndrome) coronaviruses, and it is thought to be the same with this one caused by COVID.
Our study is being done in Hong Kong, but using data from Hong Kong, the same phenomenon has actually been reported in other parts of the world.
Q,How does the super spreader occur?
A.In the case of contagious cases, you need to have a lot of people around you. If you have a contagious person who isolates himself or herself because he or she is worried about being infected, superspreader will not occur because there is no chance of contact. Also, these cases need to be relatively highly contagious. This time we found that there is a lot of variability in contagiousness.
As for the factors that contribute to the creation of superspreaders, that has not really been identified and there are probably several genetic factors. There may also be other factors related to age and social behavior.
Q, How can I reduce the number of superspreaders?
A. It would be helpful if we could find ways to minimize the chances of a superspreader event, but currently the only way to do this is to close stores, restrict entry, and ventilate. In the workplace, if there is one infected person in the middle of the floor, it is likely to spread to all the others. In public transportation, more caution may be needed for vehicles with long travel distances.
Q,Does it make sense to limit the super spreader?
A. If we can identify and eliminate super spreader events, it could help a lot in reducing infections. So, in my opinion, this is a really important approach to take. If we can reduce congestion, we can actually do a lot without having to impose a massive curfew.
Conclusion
What is a super spreader?
A superspreader is a host infected with an infectious pathogen that causes more secondary cases of infection than would normally be expected. Superspreaders are a major concern in infectious disease control and epidemiology because they can spread the infection to many other people.
From Wikipedia
Therefore, it is believed that what should be done as a countermeasure against infection is not to "restrict behavior" but to identify super spreaders as described above and avoid effective areas for infection.
The current measures are not completely useless, but if infected, individuals need to take measures to prevent the spread of the disease.
Whether the 20% of cases that spread the disease is considered a small number or a large number is up to each individual, but for me, I would rather focus on treatment than infection prevention.
Many studies on treatment have shown signs of recovery even in severe cases through trial and error, so I don't think there is a need for everyone in the world to be afraid because of the strong combination of current medical history.
In fact, some people seem to think that it is somewhere between a cold and the flu, but that doesn't mean that we should underestimate the infection, nor should we overreact.The only thing we can do is to improve our own health, and if we are infected, to act to prevent it from spreading.
