What is Contact Tracing?

Most of you have likely heard more about contact tracing in the last few weeks and months than in you had in your whole life.

You might even have been contacted by someone recently if you have been sick or exposed to COVID-19, as health professionals try and keep case counts in your area under control.

What is Contact Tracing?

Believe it or not, contact tracing wasn’t invented during the COVID-19 pandemic.

Contact tracing has long been a tool in public health to help control outbreaks of contagious diseases, from smallpox and tuberculosis to measles and HIV.

“When a person with contagious measles has travelled by aircraft, European guidelines recommend contact tracing of passengers and crew within 5 days of exposure for post-exposure prophylaxis (PEP), and within 12 days of exposure for informing passengers and crew, in order to prevent further transmissions. To be effective, contact tracing requires prompt diagnosis, immediate notification of public health authorities and rapid availability of passenger contact data.”

Thole et al on Contact tracing following measles exposure on three international flights, Germany, 2017

How does it work?

It’s actually pretty simple…

Using contact tracing, once you know that someone is sick, you:

1. Identify all of the people that they might have been in close contact while they are contagious.
2. Find these people (the case interview) and let them know of their exposure, while evaluating them for pre-exisiting immunity and risk for getting sick.
3. Review options for each contact, which might include observation, self-quarantine, post-exposure prophylaxis, or vaccination, etc.
4. Monitor contacts for signs and symptoms of the disease until they have completed a full incubation period.
5. Break the chain of transmission and stop the outbreak, as without this work, each contact could get sick, expose many other people and so on…

While that all might seem simple enough, there are many things that can complicate contact tracing, especially as the period you are contagious, incubation periods, and even what is meant by “close contact” varies with each disease.

For example, you would likely be considered a “close contact” of someone with measles if you were sitting in a room that they had left 90 minutes ago. And if you weren’t already immune, your self-quarantine would last at least 21 days – the incubation period for measles.

“For COVID-19, a close contact is defined as anyone who was within 6 feet of an infected person for at least 15 minutes starting from 48 hours before the person began feeling sick until the time the patient was isolated.”

COVID-19 Frequently Asked Questions

On the other hand, many other diseases are far less contagious or are only communicable during close skin to skin contact or sexual activity.

“Contact tracing is how you prevent cases from becoming clusters, clusters from becoming outbreaks.”

Tom Frieden – Contact tracing is a race. But few U.S. states say how fast they’re running.

Who does all of this contact tracing?

“State public health departments are hiring thousands of these workers, and experts are calling for more than 100,000 contact tracers to be deployed across America.”

You Don’t Need Invasive Tech for Successful Contact Tracing. Here’s How It Works.

Ideally it would be done by trained experts at the local or state health department.

Until that is happening routinely though, we should all learn (see courses below for the public and for health professions) how to do contact tracing and make sure it is being done on the cases we report to help keep COVID-19 case counts down.

More on Contact Tracing

• Why There is Still So Much COVID-19 Confusion
• What to Do if You Have Been Exposed to COVID-19
• How to Self-Quarantine After Being Exposed to a Disease
• Should You Be Tested for COVID-19?
• Getting Tested for COVID-19
• Contact Tracing
• COVID-19 Contact Tracing Course
• Introduction to Contact Tracing Course
• Contact Tracing for Public Health Professionals
• Temple’s Public Health Contact Tracing Training
• CDC – Resources for Conducting Contact Tracing to Stop the Spread of COVID-19
• CDC – Guidelines for the Implementation and Use of Digital Tools to Augment Traditional Contact Tracing
• CDC – Case Investigation Workflow
• WHO – What is contact tracing and why is it important?
• CDC – Contact Tracing Workflow
• CDC – COVID-19 Sample Training Plans for Contact Tracers, Case Investigators, and Supervisors
• CDC – Key Information to Collect During a Case Interview
• How far back to trace
• CDC – Case Investigation and Contact Tracing : Part of a Multipronged Approach to Fight the COVID-19 Pandemic
• CDC – HEALTH DEPARTMENTS: Interim Guidance on Developing a COVID-19 Case Investigation & Contact Tracing Plan
• CDC – COVID-19 Frequently Asked Questions
• Study – Contact tracing following measles exposure on three international flights, Germany, 2017
• Contact tracing is a race. But few U.S. states say how fast they’re running
• You Don’t Need Invasive Tech for Successful Contact Tracing. Here’s How It Works.