Recent reports have shown COVID-19 transmission prior to disease onset, raising concerns that people who appear healthy may be major contributors to the COVID-19 pandemic. Researchers at the division of neuroscience, Oregon National Primate Research Centre, Oregon Health & Science University, say that few studies have directly determined the proportion of transmission events that occur before symptom onset. But a recent modelling study by researchers at World Health Organisation Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, University of Hong Kong, inferred that 44% of secondary cases were infected during pre-symptomatic stages of disease.
They have raised questions regarding the approach and interpretation of this transmission model.
Authors
MK Slifka, L Gao
Abstract (recent modelling study)
We report temporal patterns of viral shedding in 94 patients with laboratory-confirmed COVID-19 and modelled 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’ pre-symptomatic 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 pre-symptomatic transmission.
Authors
Eric HY Lau, Gabriel M Leung
[link url="https://www.nature.com/articles/s41591-020-1046-6"]Nature article (matters arising)[/link]
[link url="https://www.nature.com/articles/s41591-020-1046-6"]Nature original article[/link]
[link url="https://www.nature.com/articles/s41591-020-1049-3"]Nature reply to (matters arising)[/link]