Dynamics of outbreaks of SARS-CoV-2 variants of concern

A study posted to the medRxiv* preprint server characterized the features of the outbreak duration of the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) variants of concern (VOCs).

The emergence of new SARS-CoV-2 VOCs throughout the coronavirus disease 2019 (COVID-19) pandemic made it challenging to control the disease outbreaks associated with variants. It is difficult to characterize the features of an outbreak due to the novelty of variants, but these variant-attributable outbreaks might share common features with previous outbreaks at other comparable locations.

Thus, it can help health bodies in regions with an imminent outbreak to make appropriate decisions and preparations for better management of the COVID-19 epidemic.

The study

In the present study, the authors analyzed data from early, documented outbreaks serving as reference points to define key features of the epidemic curve. A novel method was developed for the rapid data analysis across Europe and the United States (US) across outbreak cycles of COVID-19 caused by the SARS-CoV-2 Delta and Omicron variants.

The start dates of COVID-19 outbreaks differed across different settings. The start date for the Delta variant in India was February 2, 2021; April 4, 2021, in South Africa; and June 5, 2021, in the United Kingdom (UK). The Omicron outbreak first began in South Africa in November 2021, while the same in the US was differential due to the seasonal forcing of COVID-19 spread when infections surged in many US states.

Results

The researchers reported that the COVID-19 outbreak driven by the SARS-CoV-2 Omicron variant in South Africa followed a similar pattern observed during the Delta outbreak. The Omicron outbreak, however, was comparatively shorter than the Delta variant outbreak and, the case growth increased rapidly during the Omicron outbreak while an equally rapid decrease in COVID-19 cases was noted. In the US, Omicron outbreaks are presently seen in Hawaii, Florida, Puerto Rico, Washington D.C., and New York City, the outbreak pattern is reportedly comparable to that seen in South Africa recently.

The results show the COVID-19 outbreaks caused by the Omicron variant peak approximately one month after their onset. This observation is consistent with reports from several nations which have crossed the most adverse phase of the Omicron outbreak. These findings represent the most notable features of the Omicron outbreak and it remains to be seen if this translates into a comparable outcome for Omicron outbreaks across all locations.

Conclusions

The study findings show that regions with small populations like colleges and small communities and homogeneous jurisdictions such as cities are associated with a rapid outbreak of COVID-19 infections than large jurisdictions like the US as a whole. The duration of outbreaks can provide valuable information to make strategies for COVID-19 mitigation policies and medical logistics.

Population immunity and behavioral changes are more likely to influence the COVID-19 outbreak dynamics observed in the present study. The dynamics of immunity, either infection- or vaccine-induced, and a strain-specific biological impact like the preference for infection in upper or lower airways, among others are critical to determining the optimal requirement of medical resources. These factors are imperative in strategizing better management of COVID-19 patients infected by VOCs like the SARS-CoV-2 Delta and Omicron variants and possibly potential new variants in the future.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Tarun Sai Lomte

Tarun is a writer based in Hyderabad, India. He has a Master’s degree in Biotechnology from the University of Hyderabad and is enthusiastic about scientific research. He enjoys reading research papers and literature reviews and is passionate about writing.