Overdispersion in COVID-19 increases the effectiveness of limiting nonrepetitive contacts for transmission control

Abstract

Increasing evidence indicates that superspreading plays a dominant role in COVID-19 transmission. Recent estimates suggest that the dispersion parameter k for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is on the order of 0.1, which corresponds to about 10% of cases being the source of 80% of infections. To investigate how overdispersion might affect the outcome of various mitigation strategies, we developed an agent-based model with a social network that allows transmission through contact in three sectors: “close” (a small, unchanging group of mutual contacts as might be found in a household), “regular” (a larger, unchanging group as might be found in a workplace or school), and “random” (drawn from the entire model population and not repeated regularly). We assigned individual infectivity from a gamma distribution with dispersion parameter k. We found that when k was low (i.e., greater heterogeneity, more superspreading events), reducing random sector contacts had a far greater impact on the epidemic trajectory than did reducing regular contacts; when k was high (i.e., less heterogeneity, no superspreading events), that difference disappeared. These results suggest that overdispersion of COVID-19 transmission gives the virus an Achilles’ heel: Reducing contacts between people who do not regularly meet would substantially reduce the pandemic, while reducing repeated contacts in defined social groups would be less effective.

Lockdowns exert selection pressure on overdispersion of SARS-CoV-2 variants

“…Our recent studies have shown that the presence of overdispersion makes a pandemic far more controllable than influenza pandemics when mitigating by limiting non-repetitive contacts (17) and personal contact network size (18). We therefore speculate that restrictions which alter social contact structure may, conversely, provide a fitness advantage to variants with more homogeneous transmission, and may thus play a role in viral evolution.…”

“…a large number of social contacts. 214 These two viewpoints are complementary in obtaining a com-215 prehensive description of superspreading phenomena, rather 216 than mutually exclusive (17). Initially, 0.01% of the population is infected with the emerging variant.…”

Safety and Reverence: How Roman Catholic Liturgy Can Respond to the COVID-19 Pandemic

“…For children under 10, the risk, incidence, and severity of the disease are much smaller than in adults (Boast, 2020 ; Choi et al, 2020 ) with minor transmission risk (Boast, 2020 ; Danis et al, 2020 ; Park et al, 2020 ). Context-specificity, stochastic factors and individual level variation play a major role in the global SARS-CoV-2 spread, emphasizing strategies focused on avoiding superspreading (Althouse et al, 2020 ; Endo et al, 2020 ; Fang et al, 2020 ; Sneppen et al, 2021 ; Van Damme et al, 2020 ) rather than blanket lockdowns (Bendavid et al, 2021 ; Joffe, 2021 ).…”

The devil in the details: Herd immunity and pandemic response

“…If random events drive overdispersed transmission, we would expect that a larger proportion of the population must be immune to mitigate the local epidemic potential of these introductions. Such scenarios bring together multiple factors, overdispersion and heteroge-neous contact networks, that are beyond the calculations of a simple population immunity framework but have been shown to have an outsized impact on transmission (Sneppen et al, 2021). Considering only immunity as a control strategy, random instances of overdispersed transmission mean that the characteristics of an individual who avoids infection at one time point are not predictive of whether others who share those characteristics will avoid infection in the future; thus, targeted vaccination efforts are not possible, and a broad distribution strategy to increase overall coverage is necessary.…”