Contact Tracing


Concentration of Contact Tracing Staff per State

The Question: How many total staff do States have assigned to do contact tracing?

For example, Maine has 15+ contact tracers for every 100,000 people, 10 of them are currently assigned while the other 5+ are trained reserves. Meanwhile, they are still planning to hire almost 20 more contact tracers per 100k pop.

Proportion of Contact Tracing Staff to Daily New Cases

The Question: Are there enough contact tracers for the number of new cases reported every day?

In the same way that hospitals can be overloaded to a point of inefficiency, contact tracing is only a sustainable method of COVID-19 mitigation when the daily new cases are at or below about 10 cases per day for every 100,000 people. For states to the left of the red line, we can expect that contact tracing is still an effective method, but for those to the right of the red line, contact tracers are likely overwhelmed. The grey lines are margins that indicate the proportion of contact tracers to cases. For example, Hawaii is just above the contact tracing’s theoretical threshold of effectiveness, but has a good proportion of around 2-3 contact tracers per case.

Public Availability Information on the Number of Contact Tracers by State

The Question: Is the number of contact tracing staff in your state/territory posted publicly on a government website?

The number of active contact tracers can be a good indicator of the robustness of contact tracing programs, but few states make this information publicly available.

Public Availability Information on Contact Tracing & Transmission by State

The Question: Is data about contact tracing and transmission being posted publicly on a government website?

The data and results gathered from contact tracing can be very useful to both public health decisionmakers and individuals. These data show how well contact tracing is working and where transmission is occurring most often. This kind of information is more publicly available than the number of active contact tracers in each state but is still only available in 29% of states/territories/District of Columbia.

Prevalence of Google/Apple Exposure Notification (GAEN) Adoption by States

The Question: Are states using or planning to use Google/Apple Exposure Notification in addition to traditional manual contact tracing efforts?

Exposure notification, while still new, is another tool that states can adopt to help people take action to quarantine if they have a COVID-19 exposure.

About this page:


Contact tracing is an essential tool of the public health response to COVID-19. Successful contact tracing programs identify contacts of infected cases early and enable contacts of cases to quarantine safely. This can help break chains of transmission and reduce the burden of disease in communities, making it safer for reopening schools and businesses.

Contact tracing is a resource intensive and complicated undertaking that relies on the effectiveness of other public health interventions, including physical distancing and rapid diagnostic testing, to be successful. In communities with rising or sustained high daily incidence levels, contact tracing can become quickly overwhelmed – tracers simply cannot keep up with the volume. When incidence is below 10 cases per 100,000 population per day, contact tracing becomes more possible and can help keep control of community spread.

In April 2020, experts at the Johns Hopkins Center for Health Security estimated that at least 100,000 new contact tracers would be needed across US. The authors called for a national plan and an initiative to provide guidance and resources to state and territorial health departments to scale up and manage contact tracing programs throughout this prolonged public health crisis.

To date, very few national data have been collected on the status and effectiveness of contact tracing programs in each state. These data will allow us to understand how this intervention is working and where additional resources may be needed. The Johns Hopkins COVID-19 Contact Tracing Data Initiative seeks to fill that data gap.


The Johns Hopkins Center for Health Security has partnered with NPR, and now also Partners in Health, to collect state data on contact tracing efforts. They will continue a series of surveys that ask state and territorial public health departments questions about COVID-19 contact tracing. Selena Simmons-Duffin and colleagues at NPR fielded previous surveys in April, June, July, and September/October of 2020. Crystal Watson, DrPH, MPH, and Lucia Mullen, MPH at the Johns Hopkins Center for Health Security will continue to field surveys, to collect data every 6-8 weeks. The resulting data will be reported publicly on the Johns Hopkins Coronavirus Resource Center website. NPR will also report on the results of each survey as it is released.

Contact for Questions:

Dr. Crystal Watson, Johns Hopkins Center for Health Security: Dr. Shada Rouhani, Partners in Health: Selena Simmons-Duffin, NPR: