How Does Contact Tracing Work? An Epidemiologist Explains

The expert behind a popular Johns Hopkins course answers pressing questions

As cities and states begin to reopen, contact tracers will serve an important role in curbing the spread of Covid-19 across the country. With job options scarce right now — and the U.S. officially in a recession — contact tracing is emerging as a “fast-growing job opportunity.” Over 250,000 people have enrolled in a free course on Coursera, which teaches a person what they need to know before pursuing training as a contact tracer. The course was developed by Dr. Emily Gurley, an infectious disease epidemiologist at the Johns Hopkins Bloomberg School of Public Health.

But what exactly is contact tracing? And why is it necessary? Gurley answers these questions and more below.

Wake-Up Call: You’re an authority on this, as you’ve created this important contact tracing course for Johns Hopkins. In simple terms, can you explain what a contact tracer does?

Dr. Emily Gurley: Contact tracers find people who are infected or who have been exposed and could be infected. They make sure they know what they can do to keep from infecting other people, and help them put together a plan to prevent this — this is often referred to as isolating or quarantining.

Isolation and quarantine mean that you don’t have contact with other people while you could be infectious. This is difficult to do so contact tracers also put people in touch with resources they may need to do this successfully. It’s about people helping other people to stop the spread of Covid-19.

Most people don’t know that contact tracing has been around for a while. When else has it been used? What results has it yielded?

Contact tracing is a tried and true public health strategy to identify people who have been exposed to an infected person because they themselves may have been infected in that encounter.

The goal is to help them to change their behavior to prevent them from transmitting the infection to others, or to provide curative or therapeutic treatments. Public health departments use contact tracing to stop transmission of TB, syphilis, and HIV every day, and it’s been an important strategy in reducing the burden of these diseases. Contact tracing is also used to help stop outbreaks of infectious diseases — like measles and Ebola. Contact tracing was an important tool in stopping the recent, large outbreak of Ebola in West Africa.

As the country starts to reopen, what role will contact tracing play in the process?

If we ramp up our contact tracing programs to the scale and speed that we need to stop transmission of Covid-19, then we can feel more confident that as we open up our societies, we’re not going to suffer large increases in transmission.

We’d love to hear a bit about the course you designed. What are some of the biggest lessons you teach your students about contact tracing?

I worked with a fantastic team of people at JHSPH to put the course together. We decided what someone would need to know to be able to start training at a local health department, assuming they had no background in public health or infectious diseases.

It’s a basic introduction to the concepts of contact tracing for Covid-19. The idea was to give folks some minimal understanding of what the job is and the things they need to know to do their job including the disease and how it’s transmitted, what contact tracing is, how you do it, the ethical considerations, and how to communicate effectively with people.

Some important take-home messages for students are that: 1) This infection is transmitted very quickly, so contact tracing has to work fast; 2) Contact tracing must be done with very high ethical standards including respect for privacy and confidentiality; and 3) You must be a good communicator to do your job well — including speaking, but probably more importantly, actively listening.

What should someone expect if they get called by a contact tracer?

Well, there are two scenarios here. You could be getting a call if you’ve tested positive. Someone will be calling you to follow up on your plans to isolate yourself from others and make sure you have the resources you need to make this work. Next, they will be asking you about who you’ve had contact with since you’ve been infectious — this includes the time that you’re sick as well as the two days before you became ill. They will want to know the names and contact numbers for people you may have infected so that they can let them know about their exposure.

They will not disclose your name to any of your contacts. A contact is defined as anyone that you’ve had physical contact with, or been within six feet for more than 15 minutes, or maybe been in a room for an hour or more. If both you and the other person were wearing masks, then it might not be considered a contact. So, it’s important to realize that this is not everyone you passed on the street, or had a brief conversation with, or stood six feet away from at a checkout line.

The second scenario is that you’re getting a call because you’ve been exposed to someone who has tested positive for Covid-19. This can be a distressing call, but it’s important to know if you’ve been exposed. It’s possible that you were infected through that exposure, and that you could infect others, even before you have signs or symptoms.

So, you need to take some steps to quarantine yourself so that you don’t inadvertently infect someone else. You should expect the contact tracer to talk to you about what your plan is going to be for quarantining for 14 days since your last exposure to the case. They will likely have resources to offer you, particularly if you need assistance with getting food and medicines that you need to successfully quarantine.

Restaurants and other businesses are starting to reopen in certain places, and many Americans are likely anxious or unsure of what’s actually safe. As an infectious disease epidemiologist, what advice do you have for them? What’s safe right now and what isn’t?

We’re still learning about exactly how this virus is transmitted and more research is needed to fully assess risks. However, the evidence we have so far suggests that most transmission happens when someone has very close and long contact with someone who is infectious. For example, cases are most likely to infect the people they live with and spend a lot of time with.

This poses difficulties for stopping transmission within households but suggests that more casual contact outside the home is lower risk. There is no “zero risk” life for Covid-19, unless you truly live a life without contact with the outside world. However, current recommendations to spend time with others outdoors is a good one as transmission risk is much, much lower if you’re outside. Wearing masks indoors is a good idea so that you don’t unknowingly infect anyone else — face coverings can help protect others from you. And keep washing your hands.

Lastly, groups of people have been gathering this week for protests. What are the Covid-19 risks, if any, associated with these gatherings? How can protesters stay safe?

Again, there is no “zero-risk” life. There are risks for transmission during protests, but of course, there are also huge risks to our society if we fail to protest police brutality.

While there is some risk for transmission during protests, it is much, much less likely to happen outside. Protesters should wear masks to protect each other and try, as best as possible, to maintain some distance from each other. If you’re sick, please call about getting tested and do not attend protests if you could be infectious.

This originally appeared on Medium.