26 April 2020 – Policy Brief

SARS-CoV-2 contact tracing strategy: epidemiologic and strategic considerations

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The Government announced that a staged reduction in social distancing measures to prevent the spread of SARS-CoV-2 would begin on 27th April 2020. The reduction in transmission that has been achieved across Switzerland now needs to be maintained. A strong strategy for testing for SARS-CoV-2, contact tracing of people found to be infected, isolation of infected persons and quarantine of their contacts needs to be implemented to control the spread of infection and avoid a re-imposition of the strictest social distancing measures. Contact tracing activities need to include both classic person-based contact tracing and digital proximity tracing so that the process of identification and quarantine of contacts is quick enough to interrupt transmission. This policy brief summarises: the rationale for contact tracing and for quarantine of contacts; differences between classic person-based contact tracing and digital proximity tracing; the role of virological testing; and social and ethical considerations.

Executive summary

  • Contact tracing, followed by quarantine, is one of the key non-pharmaceutical interventions to contain the spread of infectious pathogens, including SARS-CoV-2.
  • In classic contact tracing, trained personnel interview a SARS-CoV-2 infected person, the index case, identify their contacts over a defined time period, and follow them up.
  • Digital proximity tracing is a new approach that notifies people who have been in close proximity to a SARS-CoV-2 index case, using bluetooth-enabled smartphone technology.
  • Classic person-based contact tracing and digital proximity tracing are complementary approaches that are both needed as part of a strategy to prevent and control SARS-CoV-2 because SARS-CoV-2 can be transmitted by people before they develop COVID-19 symptoms.
  • The contact tracing period for SARS-CoV-2 is from 3 days before the onset of symptoms.
  • Contacts should be quarantined for 10 days from the last possible date of exposure with an infected person.
  • Contacts could be tested by RT-PCR at the start and end of quarantine if asymptomatic, and if they develop symptoms at any time during quarantine.
  • Quarantine protocols (specifically with respect to timing and testing) need to be continually adjusted to newly emerging scientific evidence.
  • Protectionand assistance for people in quarantine need to be assured (including covering costs of testing) in order to achieve strong popular support and high compliance.
  • External accommodation, with medical supervision, needs to be available for contacts who live in a household with vulnerable people, or who cannot maintain quarantine in their own home.

Date of request: 20/4/2020
Date of response: 26/4/2020

In response to request from: Krisenstab

Comment on planned updates: updates planned

Expert groups and individuals involved: Digital epidemiology, PH, D&T, ELSI

Contact persons: