Electrical engineering

Physics

Internal medicine

Viral shedding

Pathology

Transmissibility (structural dynamics)

Virus

Disease

Coronavirus disease 2019 (COVID-19)

Infectious disease (medical specialty)

Outbreak

Engineering

Viral load

Virology

Vibration

Immunology

Quarantine

2019-20 coronavirus outbreak

Vibration isolation

Quantum mechanics

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)

Confidence interval

Medicine

Transmission (telecommunications)

Nature Medicine

We report temporal patterns of viral shedding in 94 patients with laboratory-confirmed COVID-19 and modeled COVID-19 infectiousness profiles from a separate sample of 77 infector–infectee transmission pairs. We observed the highest viral load in throat swabs at the time of symptom onset, and inferred that infectiousness peaked on or before symptom onset. We estimated that 44% (95% confidence interval, 30–57%) of secondary cases were infected during the index cases’ presymptomatic stage, in settings with substantial household clustering, active case finding and quarantine outside the home. Disease control measures should be adjusted to account for probable substantial presymptomatic transmission. Presymptomatic transmission of SARS-CoV-2 is estimated to account for a substantial proportion of COVID-19 cases.

Temporal dynamics in viral shedding and transmissibility of COVID-19