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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.

Contact tracing workflow infographic from the CDC.

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.

This February 3, 1888 article in The World highlights how contact tracing helped control smallpox.
This February 3, 1888 article in The World highlights how contact tracing helped control smallpox.

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

1 thought on “What is Contact Tracing?”

  1. Contact tracing is the only thing that works. A close analysis of data from all countries indicates that lockdowns have failed. They “flatten the curve”, as originally suggested, but they do not bring transmission rate below 1.0. Neither do masks, it appears. Ask the Asian countries how they are succeeding while keeping their society open: contact tracing. Ask China why they remain open and do not fear the virus anymore: contact tracing. Ask any of them if they want to disband their contact tracing teams and rely on masks or lockdowns. You will get some “you are crazy” looks.

    If you fail to control the outbreak with contact tracing, it will continue until herd immunity is reached.

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