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. 2023 Apr;43(4):649-659.
doi: 10.1111/risa.13736. Epub 2021 May 3.

How Asymptomatic Transmission Influences Mitigation and Suppression Strategies during a Pandemic

Adam T Biggs  1 , Lanny F Littlejohn  1
Affiliations

How Asymptomatic Transmission Influences Mitigation and Suppression Strategies during a Pandemic

Adam T Biggs et al. Risk Anal. 2023 Apr.

Abstract

Asymptomatic transmission complicates any public health strategies to combat a pandemic, which proved especially accurate in the case of COVID-19. Although asymptomatic cases are not unique to COVID-19, the high asymptomatic case rate raised many problems for developing effective public health interventions. The current modeling effort explored how asymptomatic transmission might impact pandemic responses in four key areas: isolation procedures, changes in reproduction rate, the potential for reduced transmission from asymptomatic cases, and social adherence to public health measures. A high rate of asymptomatic cases effectively requires large-scale public health suppression and mitigation procedures given that quarantine procedures alone could not prevent an outbreak for a virus such as SARS-CoV-2. This problem only becomes worse without lowering the effective reproduction rate, and even assuming the potential for reduced transmission, any virus with a high degree of asymptomatic transmission will likely produce a pandemic. Finally, there is a concern that asymptomatic individuals will also refuse to adhere to public health guidance. Analyses indicate that, given certain assumptions, even half of the population adhering to public health guidance could reduce the peak and flatten the curve by over 90%. Taken together, these analyses highlight the importance of taking asymptomatic cases into account when modeling viral spread and developing public health intervention strategies.

Keywords: Asymptomatic; pandemic; public health.

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Conflict of interest statement

The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, nor the U.S. Government. The authors are military service members or employees of the U.S. government. This work was prepared as part of their official duties. Title 17 U.S.C. §105 provides that “Copyright protection under this title is not available for any work of the United States Government.” Title 17 U.S.C. §101 defines a U.S. Government work as a work prepared by a military service member or employee of the U.S. Government as part of that person's official duties. The authors have no financial or nonfinancial competing interests in this manuscript.

Figures

Fig 1
Fig 1
Values associated with unmitigated COVID‐19 progression. Modeling values are determined based on CDC pandemic planning scenarios as of November 2020 (R 0 = 2.5, 40% asymptomatic, 10 days to resolution)
Fig 2
Fig 2
Projected peak total infection rates due to differential effectiveness of isolation procedures (Baseline model parameters: R 0 = 2.5, 40% asymptomatic, 10 days to resolution). Four projections indicate the change to R 0 as a function of isolation procedures (e.g., 25% indicates a 75% reduction in R 0, or R 0 = 2.00 × 0.25 = 0.50)
Fig 3
Fig 3
Reduced asymptomatic transmission rates for asymptomatic cases (R 0 = 2.5, 50% asymptomatic, 10 days to resolution). Four asymptomatic transmission rates were analyzed with some reduced percentage of transmission relative to symptomatic or presymptomatic cases (100%, 75%, 50%, and 25%). Only three are pictured because a 25% asymptomatic transmission rate yielded a peak total percentage infected as less than 1% of the population
Fig 4
Fig 4
Peak percentage of population simultaneously infected based on the percentage of population who adhere to public health guidance cases (R 0 = 2.5, 50% asymptomatic, 10 days to resolution). Blue line represents a 50% potency of effective reproduction rate due to public health guidelines (50% reduction), and gold line indicates a 10% potency (90% reduction) of effective reproduction rate due to public health guidelines
See this image and copyright information in PMC

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