COVID-19 Case Investigation & Contact Tracing

What is contact tracing and why is it important?
The San Francisco Department of Public Health (SFDPH) has been using contact tracing for decades as a tool to slow or stop the spread of infectious diseases. Today, SFDPH, with support from the City’s COVID Command Center, has adopted contact tracing as part of the City’s strategy to combat COVID-19.
Contact tracing slows the spread of COVID-19 by:
  • Letting people know they may have been exposed to COVID-19 and should monitor their health for signs and symptoms of COVID-19;
  • Helping people who may have been exposed get tested;
  • Making sure that people who have COVID-19 can self-isolate for 10 days; and making sure individuals who are a close contact of someone with COVID-19 self-quarantine for 14 days; and
  • Connecting people to support services including food, cleaning supplies, financial support, and more.

Help slow the spread of the disease – answer the call or text from SFDPH!

How does contact tracing work?
For contact tracing work to be effective, SFDPH needs you to answer the call or text. Everything discussed with the interviewer or entered into out online tools is completely confidential. They will never ask for your money, immigration status, citizenship, or social security number. 
Contact tracing efforts are conducted by case investigators and contact tracers in your preferred language by phone or online. These trained public health workers are equipped with specialized skills to help protect you, your family, and your community.
Case investigators will ask you about your close contacts - anyone who was within 6 feet of the infected person for a cumulative total of 15 minutes or more over a 24-hour period.
Step One: Case Interviewer provides support for COVID-Positive Individual
If you test positive for COVID-19, expect a public health worker to call or text you. Please answer. Once SFDPH learns of a new positive case, a case investigator reaches out to the person who tested positive to start a case investigation.
The case investigator will work with you in your preferred language to:
  • Help you check for symptoms;
  • Link you to care, resources to safely isolate, food services, financial support, and other wrap around services so you can isolate with minimal impact.
If you indicate in our online tool that you are able to safely isolate on your own, you might not immediately receive a follow-up phone call from the health department. If you need help isolating, we will call you as soon as possible.
Step Two: Case Interviewer requests Close Contacts of COVID-Positive Individual
Once a case investigator has offered support and resources, the interviewer or online tool will ask you to identify your close contacts: anyone who was within 6 feet of you for a cumulative total of 15 minutes or more over a 24-hour period.
A contact tracer will never share your identity – or any personal information – without your permission. That means that when we reach out to your close contacts, we won’t identify you – we will only say that they have been exposed to COVID-19 and need a test.
Step Three: Contact Tracer provides support for Close Contacts
If you are identified as a close contact, a contact tracer will reach out to you by phone call or text to let you know you may have been exposed. They will, in your preferred language:  
  • Link you to free testing resources;
  • Help you check for symptoms;
  • Give you information about how to quarantine safely and stay healthy; and
  • Link you to care, resources to safely isolate, food services, financial support, and other wrap around services so you can isolate with minimal impact.
Please note SFDPH recommends testing for all contacts, regardless of whether they had symptoms or not.
What do the case investigators and contact tracers ask? Is it confidential?
Case investigators and contact tracers will never share your personal information without your permission. They will never ask for money, your citizenship status, financial information, or your social security number. The interviewer will NOT tell you who may have exposed you to COVID-19.
When the interview is over, the interviewer will connect you to resources and give you information about what to do next. Your participation is voluntary. All information you provide is confidential and your medical information is protected by law. Interpreters are available.
Some examples of possible questions a case investigator or contact tracer might ask include:
  • What are your symptoms?
  • When did your symptoms start?
  • Who lives in your household?
  • Did you have contact with anyone diagnosed with COVID-19? Where and when do you think you were exposed to COVID-19?
  • Did you attend any recent social and large gatherings?
  • Where did you go when you were contagious?  Did you attend work or school?
  • Please provide the names and contact information for people you were in close contact with recently.
Case Investigation & Contact Tracing Data
On November 2, 2020, the SFDPH Contact Tracing Team published a research letter evaluating their contact tracing efforts from April – June 2020 in JAMA Internal Medicine. This peer-reviewed report is among the first reports of contact tracing outcomes from a local health department in the United States. Some of their important findings, updated with data from August through October 2020, are presented below.
Cascades: How Epidemiologists Track Data in Contact Tracing
Epidemiologists use contact tracing “cascades” to track data along each step of the contact tracing process.
In the cascades below, each bar represents a step in the process, beginning with a 100% bar representing the total cases or total contacts identified. Each subsequent bar then shows what percent of that original group completed the next step in the process (e.g.., what percent of all cases identified at least one close contact).
The goal of contact tracing is to identify and test as many close contacts in order to identify new cases before they have a chance to transmit to others. Therefore, an ideal cascade would include high percentages of individuals at each of the steps except the final percent testing positive.
Case Investigation Cascade
The cascade below reports on case investigation results, with the final bar revealing the percentage of cases that resulted in at least one close contact reporting a positive test. 
From August through October 2020, 15% of cases investigated resulted with one or more contacts testing positive.
Contact Tracing Cascade
The cascade below reports on the contact tracing results, with the final bar revealing the percentage of named contacts reporting a positive test. 

Of contacts identified by cases from August through October 2020, 48% of contacts were tested and 13% of contacts tested positive.  

Race & Ethnicity Cascades 
SFDPH also monitors case investigation and contact tracing cascades by race and ethnicity. Race and ethnicity are critical to track because of how institutional racism and structural inequities impact current social determinants of health. It is also important to note that the effects of COVID-19 are complex and affect all residents based on many factors, like income level, age, gender identity, sexual orientation, and more.
The cascades below with data from August through October 2020 offer useful information that should be considered alongside trends in other important data, including rates of testing, positivity, hospitalizations, cases, and deaths.
Please note that the Contact Tracing Cascade by Race/Ethnicity cannot start from all contacts, as race/ethnicity information can only be obtained when a contact tracer speaks with the contact. Not all contacts are reached.
What is the City doing to improve Contact Tracing efforts?
Since the first cases of COVID-19 were diagnosed in San Francisco during the first week in March 2020, SFDPH has proactively scaled up and trained a robust, multilingual and culturally competent contact tracing workforce. In November 2020, SFDPH added an online tool to its contact tracing efforts, making it easier to reach those residents in greatest need of City support. In December 2020, the State of California launched CA Notify, allowing mobile phone users to opt in to notifications about their possible exposure to COVID-19.
Contact tracing is a critical component of our City’s COVID-19 response, requiring collaboration with community partners to increase public awareness and understanding of case investigation and contact tracing processes. Together, we can creatively and rapidly identify new cases and ensure there are resources to test and trace contacts in our communities.
SFDPH monitors data for each of the steps in the cascades above in order to identify opportunities to improve and optimize contact tracing efforts. SFDPH is undertaking many initiatives including:
  • Hiring staff from disproportionately affected communities, with a focus on increasing bilingual staff who are culturally sensitive while interviewing cases and contacts;
  • Offering close contacts prioritized access to City-sponsored testing facilities;
  • Directly funding community-based organizations to increase outreach, prevention, tracing and wellness services;
  • Providing technical assistance to help community-based organizations develop the tools and skills to successfully implement effective COVID-response teams for people within their communities; and
  • Researching new approaches to increase rapid testing among contacts.
Data Notes
Dates are not based on specimen collection date. (Cases included above were imported into the case investigation system between August 1 and October 31, 2020. Contacts included were those identified between August 1 and October 31, 2020.) Therefore, some counts will not align with cases and contacts reported on other COVID-19 Data and Reports pages.