Ebola asymptomatic transmission1/18/2024 ![]() ![]() Objective To assess the proportion of SARS-CoV-2 transmissions in the community that likely occur from persons without symptoms.ĭesign, Setting, and Participants This decision analytical model assessed the relative amount of transmission from presymptomatic, never symptomatic, and symptomatic individuals across a range of scenarios in which the proportion of transmission from people who never develop symptoms (ie, remain asymptomatic) and the infectious period were varied according to published best estimates. Optimal control of COVID-19 depends on directing resources and health messaging to mitigation efforts that are most likely to prevent transmission, but the relative importance of such measures has been disputed. Importance Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiology of coronavirus disease 2019 (COVID-19), is readily transmitted person to person. Even with 0% infectiousness from never symptomatic individuals (highly unlikely), more than half of transmission still comes from presymptomatic indivduals if onset occurs around the time of peak infectiousness. Substantially lower estimates of relative infectiousness can therefore be considered in both Figure 1D and Figure 2. Another example with the same result is 30% never symptomatic with 20% relative infectiousness. One example of that would be 10% never symptomatic with 75% relative infectiousness (described in the manuscript). For example, Figure 1D includes 8% of transmission from those who are never symptomatic. The 75% value was used for the baseline as it lies within the range of estimates described above. 100%) among symptomatic and never symptomatic infections (Lee et al., Reference 9), (2) estimates of 40-140% based on an estimated risk ratio 95% confidence interval of 0.69-2.37 for case contacts of symptomatic versus asymptomatic/presymptomatic (Chaw et al., Reference 15), and (3) a rapid review based on six studies that inferred an approximate range of 40-70% (Mc Evoy et al., Reference 16).Ī baseline assumption was necessary to show the effects of different values of relative infectiousness and the proportion of individuals who never develop symptoms. In the manuscript, we cite three relevant estimates based on data: (1) similar viral shedding (i.e. A number of commentators have asked about the base value for the infectiousness of persons without symptoms relative to those with symptoms. We very much appreciate the robust discussion on this paper. Shared Decision Making and Communication.Scientific Discovery and the Future of Medicine.Health Care Economics, Insurance, Payment.Clinical Implications of Basic Neuroscience.Challenges in Clinical Electrocardiography.Panels D, E, and F show different proportions of transmission from individuals who are never symptomatic: 8% (C eg, 10% never symptomatic and 75% relative infectivity), 24% (D baseline, 30% never symptomatic and 75% relative infectivity), and 30% (E eg, 30% never symptomatic and 100% relative infectivity). We calibrated infectiousness to peak at day 4 (A), 5 (B median incubation period), or 6 (C) days. ![]() Panels A, B, and C show different levels of presymptomatic transmission. The portion attributed to individuals with symptoms (light blue) can also be interpreted as the maximum proportion of transmission that can be controlled by immediate isolation of all symptomatic cases. Within each curve, the colored area indicates the proportion of transmission from each class of individuals. The top curve in each panel represents the average relative hourly infectiousness, such that while the lower curves change under different assumptions, the total hourly infectiousness equals 1 in all cases. ![]()
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