Interventions targeting non-symptomatic cases can be important to prevent local outbreaks: SARS-CoV-2 as a case study

Francesca A. Lovell-Read*, Sebastian Funk, Uri Obolski, Christl A. Donnelly, Robin N. Thompson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


During infectious disease epidemics, an important question is whether cases travelling to new locations will trigger local outbreaks. The risk of this occurring depends on the transmissibility of the pathogen, the susceptibility of the host population and, crucially, the effectiveness of surveillance in detecting cases and preventing onward spread. For many pathogens, transmission from pre-symptomatic and/or asymptomatic (together referred to as non-symptomatic) infectious hosts can occur, making effective surveillance challenging. Here, by using SARS-CoV-2 as a case study, we show how the risk of local outbreaks can be assessed when non-symptomatic transmission can occur. We construct a branching process model that includes non-symptomatic transmission and explore the effects of interventions targeting non-symptomatic or symptomatic hosts when surveillance resources are limited. We consider whether the greatest reductions in local outbreak risks are achieved by increasing surveillance and control targeting non-symptomatic or symptomatic cases, or a combination of both. We find that seeking to increase surveillance of symptomatic hosts alone is typically not the optimal strategy for reducing outbreak risks. Adopting a strategy that combines an enhancement of surveillance of symptomatic cases with efforts to find and isolate non-symptomatic infected hosts leads to the largest reduction in the probability that imported cases will initiate a local outbreak.

Original languageEnglish
Article number1014
JournalJournal of the Royal Society Interface
Issue number178
StatePublished - 19 May 2021


  • COVID-19
  • SARS-CoV-2
  • asymptomatic infection
  • infectious disease epidemiology
  • mathematical modelling
  • presymptomatic infection


Dive into the research topics of 'Interventions targeting non-symptomatic cases can be important to prevent local outbreaks: SARS-CoV-2 as a case study'. Together they form a unique fingerprint.

Cite this