By now, every one has heard about “Contact Tracing.” And now, many are confused about what it really is. The term “Contact Tracing” has been used as a catch-all for the work health departments do to identify and follow up on cases.

In late February, when the US had it’s very first case of potentially community acquired COVID-19, I explained how a disease investigation works. Most of what I said then still holds true, but let’s go back to the start.

Disease Investigation

The health department receives a lab report (or, now, hundreds of them), showing a positive COVID-19 test. The lab report will have the name and usually the clinic/site that ordered the test. Ideally it’ll also have contact information for that person tested (this wasn’t always the case).

The investigation starts with the “Case Investigator.” This person calls the case — the person with the positive lab result. The case may have already heard from their doctor that their test was positive, or not. The investigator discusses the lab result.

They’ll ask all the usual demographics. When you started feeling sick. If you know you were exposed to another case. If your symptoms are mild and you don’t need hospitalization, they’ll ask if it’s possible to isolate within your home. If not, they’ll inform you so a hotel option that is paid for by the city.

Then they’ll ask where you’ve been, who you’ve been with, how long were you with them. The location matters because close contact indoors for extended periods increases the likelihood of transmission. They’ll use this information to determine your primary contacts.

They’re not contacting your employer to tell them you’ve been infected. They’re not releasing your name to anyone. Your health details are kept private.

Contact Tracing

That’s when the contact tracing part of the investigation starts. The contact tracers will call the people on your list. They’ll say “You were exposed to COVID.” They won’t say how, or where, or by whom. They’ll ask if you have symptoms, and depending on the circumstances, advise you to get a test. They’ll also tell you to quarantine for 14 days from the day of exposure. That means you don’t go out, you don’t visit with friends. You don’t go shopping. You avoid contact with others.

Locally, the city has contracted with a company to do this. The company has an app which you can voluntarily choose to use. It’s optional.

Really, this was all background to share this Twitter thread which sums up the challenges with contact tracing.

Contact tracers need to be from the affected community to establish trust. We may need to offer incentives to get people to share information — they are scared to do so, for many reasons. We need to identify those reasons so we can overcome them. Many people don’t answer the phone: we need caller ID to be clear so people answer. We need to be willing to adapt, and to be transparent.

“BIG PICTURE? @nycHealthy is ahead of just about anyone else in the country. They’ve hired ~3000 contact tracers. They’re being transparent with their data. They’re analyzing the data & improving processes along the way. THAT’S the public health approach. “


Dr. Rohr-Allegrini is an epidemiologist and tropical disease scientist currently working to prevent diseases through immunizations.

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