The effect of superspreader events on the timeline and severity of the SARS-CoV-2 pandemic
Last March, the SARS-CoV-2 virus was introduced to the United States, with the nation experiencing rapid exponential growth in cases and a total of 1.54 million deaths worldwide reported as of December 2020. The pandemic has drastically changed the lifestyles of individuals into a new normal of mask-wearing, stay at home orders, remote work and school, and social distancing. According to the CDC, social distancing is defined as keeping a safe space between yourself and other people who are not from your household. To practice social or physical distancing, individuals should stay at least 6 feet from others who are not from their household in both indoor and outdoor spaces. However, many Americans are eager for a return to normal life, making them inclined to break social distancing prior to the end of the pandemic. Some of these violations of social distancing have come in the form of large social gatherings. Oftentimes, one person at these events is unknowingly and asymptomatically infected with the virus and many attendees also become infected, thus causing a ripple effect.
This phenomenon is known as a super spreader event. Super spreading events occur when a single person infects a large number of people in one setting which then sparks a significant cluster of cases. These events happen because of a combination of biology and setting; an infected person has to be at a point in their illness when they are very transmissible and they have to be in a place where they can infect a lot of other people. Places where people are densely packed and engaging in something that involves a lot of breathing, like singing or talking, are particularly risky for super spreading. The most notable thing about superspreader events is that they are entirely preventable and could cause severe implications for a patient. Here, we detail one high-profile superspreader event that occurred in the United States during the ongoing coronavirus pandemic.
Just mere days before the 2020 presidential election, Donald Trump held a convocation for Amy Coney Barrett’s supreme court nomination in the Rose Garden. This convocation became a high-profile superspreader event, as at least eight attendees contracted the coronavirus. Attendees crowded in close proximity, shook hands, and hugged. Few individuals were seen wearing masks. While the identity of the initial spreader is unknown, “the president, First Lady, members of Congress, the White House press secretary and other staff members, members of the media, and countless employees who support the operations of the U.S. government and the Trump reelection campaign were infected by the coronavirus” (Stat News). This event caused an exponential growth of the number of cases in the US, especially throughout Washington DC.
For the purposes of understanding the implications of this event, first, we can compare the impacts of an infected patient who social distances to an infected patient that attends a social event that becomes a superspreader. The links between cases in both of these instances can be shown through a comparison of basic models, or branching processes. On each figure, red dots represent an infected individual and red lines represent the contact between infected nodes.
Figure 1. Branching process of an initial spreader when practicing social distancing
Figure 2. Potential branching process of the initial spreader at the Rose Garden super spreader event
Figure 1 is a typical representation of who an initial spreader can pass the Coronavirus to if the initial spreader follows social distancing and other public health guidelines. Specifically, it is estimated that these individuals will infect approximately 0-3 other people. This was accounted for in Figure 1 through the use of a random number generator that gave values of 0, 1, 2, or 3 randomly. The number generated represents the number of people who contracted the virus, given that each person in this cluster came into close contact with three people. Figure 2, on the other hand, is a representation of the contraction of the 2019 Novel Coronavirus at a super spreading event, in this case, the Rose Garden convocation. It is estimated that more than 200 individuals attended this event. While it is unknown who the initial spreader was or how many people they came into close contact with, news outlets estimate that they infected at least eight other individuals. Because there are some uncertainties with exact numbers, a few assumptions need to be made on the model, but the underlying results remain the same. Specifically, this model assumes that out of about 200 attendees, the initial spreader came into close contact with about 50. The 150 individuals who did not come into close contact with the infected person are drawn at the top of the figure. The other 50 who did have close contact are depicted with edges connecting to the initial spreader. Based on this model, in a best-case scenario, newly infected individuals who contracted the Coronavirus at the Rose Garden immediately isolated themselves and only infected 0-3 other individuals each. This is shown in the third line of nodes (a random number generator picked numbers 0-3 like in Figure 1 since the actual statistics are not public). This process was then repeated for the last line of nodes, and continues with each node, although it is not shown in the figure.
Figure 1 and Figure 2 each show four rounds of contact that stem from one infected person. The only difference in the figures is the presence of social distancing and mask-wearing. In Figure 1, a total of six people are infected, including the initial spreader. In Figure 2, a total of 43 people contract the virus. Each person who consequently falls ill becomes an initial spreader with new people in their social circles, so this process continues until the disease is eradicated. As clearly shown, large social gatherings largely increase the number of infected individuals and thus the severity of the pandemic. Therefore, as a result of these events, the Coronavirus remains rampant in the United States for a longer period of time. This shows why isolation is essential during times of a highly contagious pandemic.