corona virus-Covid19

How Well Did COVID-19 Contact Tracing Work in San Francisco? Interview with:

Darpun D. Sachdev, M.D. Case investigation and Contact tracing Branch Chief SFDPH Covid Command Center San Francisco Department of Public Health

Dr. Sachdev

Darpun D. Sachdev, M.D.
Case investigation and Contact tracing Branch Chief
SFDPH Covid Command Center
San Francisco Department of Public Health What is the background for this study? What are the main findings?

Response: The ultimate goal of contact tracing is to rapidly identify and isolate contacts who are COVID-19 positive before they have time to transmit to others. As mentioned in the published research letter by SFDPH, through JAMA, during early shelter-in-place (from April to June 2020), our contact tracing program successfully reached greater than 80% of cases and contacts within a median timeframe of 6 days from the onset of their case’s symptoms. Approximately 10% of named contacts were newly diagnosed with COVID-19 (compared to 2% positivity during this time period). Household contacts made up approximately 80% of all identified contacts, but 90% of contacts who tested positive lived in the same household as the case. Secondary cases (contacts who were found to be newly diagnosed with COVID-19) were traced and quarantined within 6 days of the case’s symptom onset.

With that said, the 6-day time difference between symptom onset and contact notification raises concern regarding the overall effectiveness of tracing in preventing onward transmission by infected contacts. We are working with community-based organizations to scale up access to testing and culturally competent tracing and wraparound services. Currently, we have now decreased the time difference to 5 days. Moreover, given that the majority of contacts resided in the same household, transmission could have occurred presymptomatically such that by the time infected contacts were identified, they might have already transmitted the virus. Hence, why SFDPH, on May 5, 2020, implemented the recommendation of universal testing for COVID-19 contacts, regardless of symptoms.

We recommend that testing should be offered to all contacts regardless of symptoms and encourage local health departments to adopt novel ways of increasing testing access for contacts. What should readers take away from your report?

Response: In addition, this research letter presents the contact tracing continuum and breaks down contact tracing process into key measurable steps. This cascade can help standardize metrics and increase transparency on the success of and opportunities to improve contact tracing. Although participation is voluntary throughout the contact tracing process, it is important for cases and contacts to pick up the call from the health department and understand that their cooperation to isolate and quarantine is critical to helping slow the spread of the virus. Partnership between the community and health departments is critical in the success of reaching cases and contacts and increase of the proportion of them engaging with contact tracing, reporting close contacts and being connected to support wraparound services.

As this research letter highlights the above findings, it also recognizes the need to further improve outcomes along each step of the contact tracing cascade, to identify ways to increase the number of contacts identified, and to ensure testing for all contacts in order to maximize the number of people newly diagnosed with COVID-19. In order for further research to be conducted, more data are needed to understand how to decrease the time from case’s symptoms to contact notification and testing.

All in all, SFDPH’s experiences and successes shared in this research letter offer both a benchmark for other health departments as well as a framework and metrics for evaluation.


Outcomes of Contact Tracing in San Francisco

Sachdev DD, Brosnan HK, Reid MJA, et al. Outcomes of Contact Tracing in San Francisco, California—Test and Trace During Shelter-in-Place. JAMA Intern Med. Published online November 02, 2020. doi:10.1001/jamainternmed.2020.5670 


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Last Updated on November 2, 2020 by Marie Benz MD FAAD