How do different social settings impact super-spreading event formation and onward transmission generation?

By Shanet Susan AlexAug 22 2022Reviewed by Danielle Ellis, B.Sc.

In a recent study posted to Preprints with The Lancet*, researchers analyzed the influence of nightlife environments in sustained coronavirus disease 2019 (COVID-19) transmission.

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources

Background

One characteristic feature of COVID-19 is the overdispersion in producing secondary cases. The investigation of actual COVID-19 outbreaks and modeling research revealed that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) propagation requires numerous super-spreading events (SSEs) among transmission chains.

There have been numerous case reports of SARS-CoV-2 outbreaks at nightlife venues, including bars and restaurants, throughout the SARS-CoV-2 pandemic, including those caused by the Omicron and Delta strains. Indeed, case studies are the primary data source supporting nightlife venues as high-risk environments for subsequent viral transmission. Moreover, research employing extensive, real-world epidemiological information on the varied interconnectivity of SSEs happening in various social circumstances is scarce.

About the study

In the current research, the investigators pioneeringly used extensive, real-world epidemiology data to examine the effects of various social contexts on the generation of SARS-CoV-2 SSEs and successive viral transmission. They sought to comprehend the many SSE traits and how they connect to onward SARS-CoV-2 community transmission to enlighten balanced, effective, and targeted efforts to stop the COVID-19 spread.

The scientists evaluated 44,054 confirmed SARS-CoV-2 cases in Tokyo, Japan, between 23 January 2020 and 5 December 2020, using information from thorough epidemiological studies conducted by public health facilities. They discovered epidemiological connections in these cases and divided their occurrences into seven distinct venues for transmission: nightlife, healthcare (such as hospitals and long-term care institutions), imported, dining, household, workplace, and others.

The team examined the temporal correlations of COVID-19 cases recognized in transmission environments, variables linked to onward transmission, and age matrices of preliminary and offspring patients utilizing information from thorough epidemiological analyses in Tokyo to explain elements connected to the development of SSEs and subsequent viral spread.

Results

The team uncovered transmission venues in 13,122 COVID-19 cases, including 2,733 healthcare, 1,174 nightlife, and 6,768 household cases.

The study results identified almost 6600 potential SARS-CoV-2 transmission sites, with the likelihood of five cases or more occurring in healthcare and nightlife environments. While nightlife SARS-CoV-2 incidents appeared during the initial stage of COVID-19 epidemics, healthcare and household cases emerged later.

Relative to the average date of commencement of nightlife-linked COVID-19 instances, healthcare-associated cases (16 and 40 days after in the first wave and second wave, respectively) and household cases (10 and 35 days after in the first wave and second wave, respectively) lagged in both pandemic waves. The authors mentioned that in SARS-CoV-2 pandemic waves 1 and 2, the temporal pattern of cases favored nightlife settings immediately and household and healthcare environments afterward.

Healthcare and household cases were least likely to cause subsequent spread than cases from nightlife after controlling for the transmission environment, age group, sex, pandemic wave, and the existence of a symptom. There were rarely many cases within household settings, and there was little chance of a subsequent transmission from household cases. Furthermore, the scientists found that while household environments promoted intergenerational virus transmission, non-household settings, such as nightlife, chiefly encompassed viral spread among the same age category, particularly across younger cohorts.

Together, the study data imply that 1) nightlife environments are what cause COVID-19 transmission and 2) while healthcare and household contexts have an impact on individuals that are more at risk of mortality, they are unlikely to cause further transmission.

Conclusions

Overall, the present work described contributors to and characteristics of SARS-CoV-2 spread between cases associated with transmission environments.

According to the study findings, in Tokyo, the nightlife environment steered the first two COVID-19 epidemics in 2020. On the other hand, the healthcare and household settings were at the bottom of the transmission chain and had a higher likelihood of experiencing disruptions in SARS-CoV-2 transmission chains. Besides, although the current study focused on the dynamics of SARS-CoV-2 transmission in Tokyo, the researchers believe that the crucial role of nightlife environments as the primary catalyst for COVID-19 spread was transferable across nations and viral variants.

Additionally, the authors suggested that policies aimed at nightlife environments would be a good choice for well-balanced initiatives for controlling COVID-19. Therefore, countermeasures and surveillance addressing the nightlife conditions should be prioritized to stop SARS-CoV-2 transmission, particularly in the early stages of an epidemic or a resurgence of cases, and limit it from reaching groups with high mortality risk.

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources