Onset and window of SARS-CoV-2 infectiousness and temporal correlation with symptom onset: a potential, longitudinal, group cohort research



Information of the window of SARS-CoV-2 infectiousness is essential in growing insurance policies to curb transmission. Mathematical modelling based mostly on scarce empirical proof and key assumptions has pushed isolation and testing coverage, however real-world information are wanted. We aimed to characterise infectiousness throughout the total course of an infection in a real-world group setting.


The Evaluation of Transmission and Contagiousness of COVID-19 in Contacts (ATACCC) research was a UK potential, longitudinal, group cohort of contacts of newly identified, PCR-confirmed SARS-CoV-2 index instances. Family and non-household uncovered contacts aged 5 years or older had been eligible for recruitment if they might present knowledgeable consent and conform to self-swabbing of the higher respiratory tract. The first goal was to outline the window of SARS-CoV-2 infectiousness and its temporal correlation with symptom onset. We quantified viral RNA load by RT-PCR and infectious viral shedding by enumerating cultivable virus day by day throughout the course of an infection. Members accomplished a day by day diary to trace the emergence of signs. Outcomes had been assessed with empirical information and a phenomenological Bayesian hierarchical mannequin.


Between Sept 13, 2020, and March 31, 2021, we enrolled 393 contacts from 327 households (the SARS-CoV-2 pre-alpha and alpha variant waves); and between Might 24, 2021, and Oct 28, 2021, we enrolled 345 contacts from 215 households (the delta variant wave). 173 of those 738 contacts had been PCR optimistic for multiple timepoint, 57 of which had been at the beginning of an infection and comprised the ultimate research inhabitants. The onset and finish of infectious viral shedding had been captured in 42 instances and the median period of infectiousness was 5 (IQR 3–7) days. Though 24 (63%) of 38 instances had PCR-detectable virus earlier than symptom onset, solely seven (20%) of 35 shed infectious virus presymptomatically. Symptom onset was a median of three days earlier than each peak viral RNA and peak infectious viral load (viral RNA IQR 3–5 days, n=38; plaque-forming models IQR 3–6 days, n=35). Notably, 22 (65%) of 34 instances and eight (24%) of 34 instances continued to shed infectious virus 5 days and seven days post-symptom onset, respectively (survival chances 67% and 35%). Correlation of lateral move system (LFD) outcomes with infectious viral shedding was poor throughout the viral progress section (sensitivity 67% [95% CI 59–75]), however excessive throughout the decline section (92% [86–96]). Infectious virus kinetic modelling steered that the preliminary fee of viral replication determines the course of an infection and infectiousness.


Lower than 1 / 4 of COVID-19 instances shed infectious virus earlier than symptom onset; beneath a crude 5-day self-isolation interval from symptom onset, two-thirds of instances launched into the group would nonetheless be infectious, however with lowered infectious viral shedding. Our findings assist a job for LFDs to securely speed up deisolation however not for early analysis, until used day by day. These high-resolution, community-based information present proof to tell an infection management steering.


Nationwide Institute for Well being and Care Analysis.


Widespread group transmission of SARS-CoV-2 continues to happen, even in populations with excessive ranges of immunity. Lowering transmission stays central to the general public well being response; nonetheless, as virus circulation turns into endemic, there’s a want for a realistic strategy, ideally limiting self-isolation to the period of infectiousness. Delineation of the window of infectiousness and the way the diploma of infectiousness adjustments with time since an infection, symptom onset, and diagnostic take a look at outcomes is due to this fact elementary to growing a greater understanding of transmission and simpler, evidence-based an infection management insurance policies.

Mathematical modelling based mostly on scarce empirical proof and key assumptions has considerably pushed isolation and testing coverage internationally.


  • Quilty BJ
  • Clifford S
  • Hellewell J
  • et al.
Quarantine and testing methods in touch tracing for SARS-CoV-2: a modelling research.