Once states have lower COVID-19 case rates for at least 14 days, widely available testing, and adequate medical/hospital resources, contact tracing becomes an important strategy to eliminate transmission of SARS-CoV-2, the virus that causes COVID-19. Contact tracing involves multiple steps, including case investigation of COVID-19 clients, notification of close contacts, and daily monitoring of close contacts. This process can be labor-intensive, and communities have different circumstances that affect contact tracing activities. These factors include the number of persons diagnosed with COVID-19 each day, number of contacts per patient, and the amount of time and resources needed to reach and follow the clients and contacts. The number of contact tracers needed is large and will vary by community. Each community will need to examine local case load and other factors to estimate how many contact tracers will be needed.
Mathematical modeling tools can be used to help estimate the number of contact tracers needed. These models require data to quantify each part of the process. The data used may differ among communities and over the course of the pandemic, which may lead to large differences in estimates from different models – or from the same model if using different values. Each community will need to determine some key parameters to be in the model. Local tuberculosis / sexually transmitted disease contact tracers are likely familiar with community-specific “inputs” regarding the average number of contacts per case and how difficult contacts are to find.
CDC does not endorse the use of a specific model; however, these tools may be used to guide planning and calculate resources needed under different scenarios. Each community should carefully incorporate as much knowledge about its situation as possible to estimate the number of contact tracers needed.
Content describing non-CDC tools in this document is provided for informational purposes only and is not intended to indicate endorsement, actual or implied, of the tools. Additionally, information on this site is provided “as is,” for users to evaluate and make their own determination as to their effectiveness.
Example using an available tool: Contact Tracing Staffing Tool – Resolve to Save Livesexternal icon
This model is built into an Excel workbook and requires input on the following values:
- # new COVID-19 clients / day
- # close contacts / COVID-19 patient
- Proportion of clients who are easy / hard / hardest to reach (and never reached). The amount of time needed to arrange and conduct the initial interview with the index patient can vary.
- Average time needed for patient investigation for each patient category
- Proportion of contacts who are household/easy/hard/hardest to reach (and never reached). Some contacts might live with the patient; other contacts might lack contact information and require fieldwork to identify.
- Average time spent on contact notification for each contact category
- Proportion of clients who can be followed in a mostly automated way versus those who need more staff time. For instance, contacts self-reporting their symptoms via email or text messages require much less time than contacts requiring daily telephone calls.
- Average amount of time spent on contacts for each day in each category
- Days spent following contacts (e.g., 14 days after exposure)
- Staffing considerations:
- Hours of daily productive work per contact tracer
- Number of workdays per week per contact tracer
- Number of contact tracers per manager
Changing the parameters in the model will change the estimated total staffing needed, even when keeping the number of daily new COVID-19 patients constant. (Note that this model does not specify overall population size. The total amount of work is proportional to the number of COVID-19 clients and contacts identified in each community rather than the total number of people living in the community.)
|Model developed by Resolve to Save Lives||Assumed daily COVID-19 Incidence/ 100,000 persons||Contact tracing staff needed / 100,000 persons||Notes or assumptions|
|Contact Tracing Staffing Calculator -Lower estimate (See below)||9*||33||5 contacts per patient; contact tracers work 8 hours/day; contacts easy-to-reach; many contacts use app/email to report daily.|
|Contact Tracing Staffing Calculator – Higher estimate (See below)||136**||3,739||20 contacts per patient; contact tracers work 7-hour days; contacts harder to reach, take longer to interview, most require calls each day.|
*Between April 15-23, 2020, the daily incidence of COVID-19 in the United States ranged between approximately 8 and 9 per 100,000 (between 25,858 and 29,916 new COVID-19 patients per day; assume US population of 328M).
**Approximate peak daily incidence of COVID-19 in New York City (approx. 11,400 incident new patients on 4/15/2020, assume NYC population of 8.4M).
Additional Considerations for Estimating Contact Tracing Resources
There are numerous factors that could affect contact tracer staffing needs that should be accounted for when estimating contact tracer needs:
- These estimates do not necessarily include all managers or additional professions needed.
- Increased case finding and testing efforts, as well as relaxing mobility restrictions could lead to more daily COVID-19 clients and/or contacts, which would require tracing resources.
- Effective contact tracing could reduce the number of new COVID-19 clients and contacts over time.
- Time from diagnosis to isolation for the index patient with COVID-19 will affect the number of contacts exposed and needing follow-up.
- Use of digital contact tracing toolspdf icon could improve workflow efficiency or allow automated messages/contact self-report of symptoms to save contact tracer effort.
- These models do not necessarily apply to special populations such as people in prisons or long-term care facilities.
This information will be updated as more tools become available.