SARS-CoV-2 is a novel coronavirus that causes the disease COVID-19. The virus spreads primarily through respiratory droplets that are generated when someone with the virus coughs, sneezes, or talks.

For some people, COVID-19 may not cause any symptoms. In other cases, it may be limited to respiratory symptoms, or it may develop into a serious systemic disease including respiratory failure, kidney and heart injury, blood clots, rashes, and more.

SARS-CoV-2 can spread easily between people, even if no symptoms are present. On average, it’s estimated that one person with the virus can potentially spread it to 2.5 other people.

Because of this, it’s important to be able to track the spread of COVID-19 within our communities. One way to do this is through contact tracing.

Let’s take a closer look at what contact tracing is, how it works, and how it can help combat the spread of COVID-19.

Contact tracing is a process that’s used by public health departments to help curb the spread of an infectious disease, such as COVID-19, within a community.

It involves identifying individuals who have contracted the disease as well as the people they’ve come into contact with. These individuals are called contacts.

Once contacts are identified, public health workers notify them of a potential exposure, and work with them to help prevent further spread of the disease. This typically involves a period of self-isolation.

Contact tracing has been used in the past to help contain outbreaks of SARS and Ebola. It’s also routinely used to control infectious diseases such as tuberculosis and sexually transmitted infections (STIs).

During the COVID-19 pandemic, contact tracing has also seen success in helping to contain outbreaks in Singapore and South Korea, as well as smaller case clusters in Italy.

Let’s look at the different steps involved in contact tracing. We’ll use COVID-19 as an example.

Step 1: Tracing

If you’re diagnosed with COVID-19, a public health worker called a contact tracer will get in touch with you to help identify your contacts. This is often done via a phone interview. During this interview, the contact tracer will ask you about your activities prior to your diagnosis.

There are also other ways that a contact tracer can track down contacts. For example, if you live in a long-term care facility, the contact tracer may ask that facility for a list of residents, visitors, and employees that were present during the potential exposure period.

Step 2: Notification

Once the contact tracer has identified your contacts, they will notify them.

If you’ve been in contact with someone with COVID-19, you may receive a call from a contact tracer at this point.

Step 3: Support and monitoring

Once contacts have been notified about potential exposure to the new coronavirus, the contact tracer will provide them with additional information on risks and next steps.

Now let’s get into what happens when you get a call from a contact tracer.

If you have COVID-19

If you have COVID-19, a contact tracer may call you to determine who your contacts were in the period during which you may have passed the virus to others. They’ll also request that you self-isolate if you haven’t been doing so already.

The Centers for Disease Control and Prevention (CDC) defines a contact as anyone who has been within 6 feet of you for at least 15 minutes, beginning 2 days before your symptoms appeared, and lasting until you were isolated.

The contact tracer will ask you questions about your activities during this timeframe. For example, they may ask you about:

  • people you’ve been in close contact with, such as family members, friends, or co-workers
  • any locations you’ve visited, including but not limited to work, school, healthcare facilities, grocery stores, and places of worship
  • if you’ve used any form of mass transit, such as air travel, the subway, or a bus route

The contact tracer will then go on to notify your contacts of a potential COVID-19 exposure. It’s important to remember that the contact tracer will not reveal your name or any other personal information to the contact they’re notifying.

Additionally, the contact tracer will likely check in with you periodically during your isolation period. The purpose of this is to see how you’re doing and to make sure your symptoms aren’t getting worse, as well as to see if you’re maintaining isolation.

If you’re a contact of someone with COVID-19

If you’re identified as someone who has been in contact with a person who has COVID-19, you will likely get a call from a contact tracer.

Some of the points the contact tracer will discuss with you during this call include:

  • Exposure risk. They will notify you that you may have been exposed to COVID-19. However, the contact tracer will not reveal any personal details about the person who’s been diagnosed with COVID-19 with whom you may been in contact.
  • Testing. They will suggest that you get tested for COVID-19. They may refer you to a testing location near you.
  • Isolation. They will request that you self-isolate for 14 days, beginning on your last day of potential exposure to COVID-19. They can give you information on resources that may help you during this period.
  • Symptoms. They will give you information on COVID-19 symptoms to look out for. They will also explain the steps you can take if you become ill.

The contact tracer may check in on you in the future to see if you have developed any signs of illness and to ask whether you self-isolated.

Any discussion that you have with a contact tracer is kept private within legal requirements.

If you’re diagnosed with COVID-19, the contact tracer will not share any personal information with your contacts. They will simply inform them of a possible exposure, and then go on to discuss next steps and monitoring.

There are some cases where others may need to know the details related to your discussion with the contact tracer. An example of this is your healthcare provider. In these specific cases, your personal or medical information may be shared.

Each state or county collects and stores this information in its own way. If you have concerns about your privacy, don’t hesitate to ask the contact tracer what steps are being taken to keep your information private.

You may have heard about contact tracing that utilizes technology as opposed to more conventional methods. Some countries, such as China and South Korea, have started using a person’s phone to track their location and potential contacts.

However, when we discuss using technology for contact tracing, it is often in the context of mobile apps. There are several methods that can be used for tracking via mobile apps:

  • Bluetooth. The app can use Bluetooth technology to assess the distance between smartphones and determine if you were near someone with COVID-19.
  • Location-based. The app can use a combination of GPS data, cell phone network data, or Wi-Fi signals to identify if you’ve been near someone with COVID-19.
  • Quick response (QR) codes. The app allows users to scan QR codes at specific locations to create a log of places they’ve been. This can then be used to assess if you may have been in the same area as someone with COVID-19.

A big advantage for using apps for contact tracing is speed. Conventional contact tracing can be time-consuming, but an app has the potential to notify contacts quickly following a positive test result.

One of the biggest limitations to digital contact tracing is that its effectiveness is heavily dependent on how many people download and use the app. If this doesn’t happen, digital contact tracing can be incomplete and less effective.

While digital methods may help with the efficiency of contact tracing, there are also concerns about privacy. To address this, many different privacy protection methods are being explored.

One of these methods involves using temporary identification codes instead of your personal information. With this method, your phone broadcasts a temporary code while also collecting codes that are broadcast from other phones in your area.

If you were to test positive for COVID-19, you could choose to upload a list of your temporary codes to a server managed by public health officials. An exposure notification would then be sent to the phones of users who had collected your temporary code.

There are some potential limitations that can make contact tracing less effective at limiting the spread of COVID-19.

Characteristics of COVID-19 transmission

The virus that causes COVID-19 can be spread regardless of whether symptoms are present in the individual who has the infection.

This can pose a problem for contact tracers, as contact tracing often focuses on identifying and isolating those with symptoms.

Testing delays

Testing delays can have a large impact on the effectiveness of contact tracing. The longer it takes to get testing results, the longer it can take to identify positive COVID-19 cases and their contacts.

One study found that reducing the delay between symptom onset and getting test results was the most important factor for improving the effectiveness of contact tracing.


Even if testing delays aren’t an issue, conventional contact tracing can be time-consuming.

Additionally, if COVID-19 is spreading rapidly through a community, it may be difficult to do contact tracing in a timely manner.


Conventional contact tracing requires trained personnel to be successful. If an area doesn’t have enough contact tracers to meet demand, it can slow down the contact tracing process.


Some people may not respond to a call from a contact tracer. This can hamper the ability of contact tracing to prevent further spread of COVID-19.

Here are some steps you can take to boost the effectiveness of contact tracing during the COVID-19 pandemic:

  • Work with contact tracers. If a contact tracer contacts you after a COVID-19 diagnosis, work with them to discuss your recent contacts and activities as thoroughly as possible.
  • Isolate yourself. If you have COVID-19 or are notified that you may have been exposed, make plans to self-isolate as directed by the contact tracer.
  • Communicate with your contacts. If a contact tracer calls you about a potential COVID-19 exposure, reach out to people who you’ve recently been in contact with so that they can take precautions and possibly get tested.
  • Report when you are ill. Contact your healthcare provider if you develop symptoms of COVID-19. They can help arrange for you to be tested.
  • Practice physical distancing. By practicing physical distancing (also called social distancing), you can limit the number of people you come into contact with. This can make contact tracing easier, should you become ill with COVID-19.

Contact tracing is used to limit the spread of a contagious disease. It works by identifying people who have the disease as well as their recent contacts. These contacts are then notified and directed to self-isolate.

If you have COVID-19, a contact tracer may call you to ask about people you’ve been in contact with and any locations you may have visited. It’s important to try to answer their questions to the best of your ability.

If you’re a contact of someone with COVID-19, a contact tracer may call you to let you know that you may have been exposed to the virus. They’ll request that you self-isolate. They can also help arrange for you to be tested.

There are limitations to contact tracing during COVID-19, such as asymptomatic spread of the virus and testing delays. You can help improve contact tracing by working with contact tracers, practicing physical distancing, and letting your healthcare provider know when you’re sick.