COVID-19 pandemic super-spreaders

An illustration on how super-spreaders impact in CoVid-19

2020 coronavirus pandemic super-spreaders are event or individuals infected with Coronavirus disease 2019 who can maximize their impact on other individuals. The term "super-spreaders" was coined by Lloyd Smith in 2005, where a small percentage of individuals controls the transmission of the infection in a large susceptible population resulting from interaction with others. Super-spreaders are of particular concern to public health authorities while dealing with the pandemic. The criteria for identifying super-spreaders are complicated with some related to biology. A person may get infected with a strain of a virus that can stay in the hosts body for longer duration and spreads easily or one having a weak immune system which allows the infection to spread for longer periods. An observation made during the 2003 SARS outbreak in Hong Kong noted that a person suffering from another disease could also become a super-spreader. The main objectives of public health authorities in such cases during a pandemic is to identify a few percentage of individuals, who could become probable super-spreaders and control the infections in the rest of the population.

Identifying super-spreaders

There are evidence-based studies conducted by scientists that identify and define the event or an individual as a super-spreader. The study performed by Woolhouse et al. suggests 20% of infected individuals are capable of spreading the infections to at least 80% of the population. To identify the severity of the outbreak, a mathematical function known as the basic reproduction number represented by R₀ is used. It is a variable which indicates the probable number of infections a person could spread while interacting with the rest of the population. There are mainly three scenarios in the spread or decline of infectious diseases:

• If R₀ is less than 1, each host is capable of infecting less than one new infection among the contact and the disease eventually dies out.
• If R₀ is equal to 1, each host is capable of infecting one more from the population. In such cases, the disease persists with stable numbers but there is no outbreak.
• If R₀ is more than 1, each host is capable of infecting more than one individual. In such cases, the prevalence of the disease increases and an epidemic may occur.

For example, some studies conducted during the SARS outbreak, though the Reproduction ratio i.e. (R₀) for the same was at 2.75; however, it was estimated that super-spreaders could infect more than 10 individuals from a susceptible population with various means of contact, even though the super-spreader may be asymptomatic. As most of the studies conducted have considered all individuals having same transmission rate and have assumed of homogeneous mixing among populations, thus arriving at a standardized form of R₀; However, (Stien, 2011) argues most studies do not take in to account the diverse characterstics of transmission rate among different hosts of the virus, which would enable public health officials to identify the super-spreading events and control the infection.

Many scientific organizations have estimated R₀ for Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19. The Imperial College group announced an R₀ ranging from 1.5 to 3.5, whereas The Lancet estimated it to be around 1.6 to 2.6 before travel restrictions were imposed in China in January 2020.

Effects of COVID-19 super-spreaders

As the main cause of transmission of this virus is contact between person to persons. Super-spreaders are of major concern since the virus from the exhaled droplets of a person infected can remain on the surface for several days. Studies conducted during the SARS pandemic showed that when there were no super-spreaders, most individuals infected very few secondary contacts. However, when a microbe infects a patient its remains contained within the host, but when it finds a super-spreader, it infect many individuals. Arriving at an accurate R₀ is difficult for various reasons, such as the properties of the pathogen-like basic life of infection and asymptomatic cases."Eisenberg 2020" /> Even though R₀ for COVID-19 ranges from 1.0 to 3.0, a super-spreader could potentially infect 10 or more people they come in contact with. Amajor issue is dealing with asymptomatic individuals infected with COVID-19, as they may unintentionally transmit the disease to many people. It is estimated that some asymptomatic individuals have infected a sizable population. It is a well-known fact that, most of the current infections of COVID-19 are travel-related and large outbreaks result primarily within health-care settings and closed community gatherings.

Information on the CoVid-19 and its impact are reviewed and updated regularly as we write. Unrecognized cases and misdiagnoses are some common causes for super-spreaders. Voluntary disclosure of the travel and contact history from the infected patients and active surveillance of the contacts is essential to negate the possibility of few becoming super-spreaders. However, super-spreading is a normal feature of disease spread.

See also

• Super-spreader
• COVID-19 pandemic

Further reading

• Allen C Cheng; Deborah A Williamson (March 2020). "An outbreak of COVID-19 caused by a new Coronavirus: What we know so far" (PDF). Insightplus.

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