Is the Increased Transmissibility of SARS-CoV-2 Variants Driven by within or Outside-Host Processes?

  1. Yehuda Arav
  2. Eyal Fattal
  3. Ziv Klausner

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Abstract

Understanding the factors that increase the transmissibility of the recently emerging variants of SARS-CoV-2 can aid in mitigating the COVID-19 pandemic. Enhanced transmissibility could result from genetic variations that improve how the virus operates within the host or its environmental survival. Variants with enhanced within-host behavior are either more contagious (leading infected individuals to shed more virus copies) or more infective (requiring fewer virus copies to infect). Variants with improved outside-host processes exhibit higher stability on surfaces and in the air. While previous studies focus on a specific attribute, we investigated the contribution of both within-host and outside-host processes to the overall transmission between two individuals. We used a hybrid deterministic-continuous and stochastic-jump mathematical model. The model accounts for two distinct dynamic regimes: fast-discrete actions of the individuals and slow-continuous environmental virus degradation processes. This model produces a detailed description of the transmission mechanisms, in contrast to most-viral transmission models that deal with large populations and are thus compelled to provide an overly simplified description of person-to-person transmission. We based our analysis on the available data of the Alpha, Epsilon, Delta, and Omicron variants on the household secondary attack rate (hSAR). The increased hSAR associated with the recent SARS-CoV-2 variants can only be attributed to within-host processes. Specifically, the Delta variant is more contagious, while the Alpha, Epsilon, and Omicron variants are more infective. The model also predicts that genetic variations have a minimal effect on the serial interval distribution, the distribution of the period between the symptoms’ onset in an infector–infectee pair.

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  1. Version published to 10.3390/math10193422
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    SciScore for 10.1101/2021.07.19.21260707: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

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  3. Version published to 10.1101/2021.07.19.21260707v1 on medRxiv