As of Friday afternoon, five people have tested positive for COVID-19 in NYC, and an estimated 2,773 people are under quarantine citywide. In what is looking like a case of community spread, "disease detectives," medically trained public health professionals, have been working to track the close contacts of people infected.

We spoke to Dr. Neil Vora, a medical epidemiologist for the Centers for Disease Control and Prevention who is based at the New York City Health Department. Last year, he managed the city’s response to a measles outbreak.

You obviously have a very cool title. Can you break down what a disease detective does?

I trained at the Centers for Disease Control and Prevention in this program called the Epidemic Intelligence Service. And it's really what we describe as shoe-leather epidemiology or interventional epidemiology.

We are field epidemiologists and disease detectives. We're a group of people who work in applied public health, meaning that we respond to and we go out in the field, if necessary, to track down cases and contacts and and implement control measures to stop outbreaks.

Generally, our strategy is the the sooner we identify an outbreak, the more effective our response will be, because we want to stop an outbreak as quickly as possible to prevent it from getting too big.

So once you identify someone who has the virus, let’s say, as in the case of the Westchester lawyer, or the two recently identified cases in New York City, then what?

We use a variety of different mechanisms. The first thing to emphasize is that surveillance, which is the detection of a set of diseases of interest, is the backbone of public health and we can't do our work in public health without good surveillance. So when we do identify a case, one of our main areas of concern is to do contact tracing around that case so we can quickly implement control measures and hopefully prevent other people from getting ill, or at least monitor some of those contacts. In the event that we do not have a specific intervention for those individuals, but monitor them so that if they do get sick themselves, we can help them get care quickly.

At the end of the day, our main goal is to keep people healthy at the population and at the individual level.

And what are the range of directives that you might give somebody who was in contact with an infected person. What happens next?

So one of the first things that we do when we identify a contact is we try to risk-stratify them because we use CDC guidance to help us determine their level of risk of getting covered. And the CDC has really clear guidance on their website about who qualifies as a high-risk or a medium-risk or a low-risk individual. And depending on their risk stratification that, well, we'll do different things.

So some individuals, if they're in a higher risk category should undergo active monitoring. We'll do daily outreach to the person, ask them to call into us daily to report a temperature and symptoms. Some people fall into that category, and that's been done for other infectious diseases before, such as Ebola back in 2014.

There are other people who fall into a lower-risk category who we might not necessarily have to do daily, active monitoring. But for them, we say, 'Stay home, try to self-quarantine yourself or and if you do develop symptoms, call us at this number, so that we can help you get the care that you need.'

So it really depends on someone's risk level. But when one of these contacts develops symptoms, we want to very quickly identify them and get them into the appropriate care that they need.

Have you begun to do contact tracing on the two cases announced Thursday?

I can't go into the specifics of any particular case investigation or contact investigation right now.

But, you know, for us, a priority is that we quickly identify cases. And one of the really good pieces of news is that we have the ability in New York City to do testing for coronavirus because we have an amazing public health lab in downtown Manhattan. And so we can test New Yorkers for a coronavirus, particularly if they fall into a higher-risk category, as they have known exposures or they have other concerning findings.

Public health is a team sport, and especially in this area of the country where there's a lot of inter-jurisdictional travel for work purposes or for school. We work together, we're in touch with other health departments and we do all of our work collaboratively.

Can you talk about what "self-quarantine" or "isolation" is?

So I want to draw a distinction between the term quarantine and the term isolation, because in public health and medicine, they mean very different things. Isolation means the separation of an individual from the rest of the population when an individual is exposed to a pathogen and is symptomatic. Quarantine refers to separation of an individual from the rest of the population when an individual does not have symptoms but might have been exposed to a pathogen. And so certain people we are advising, ‘Well, you've come back, but you're in a lower risk category.’ So we just asked you to voluntarily stay at home. Other people who fall into a higher risk category might be asked to quarantine in their home. But certainly whenever anyone with any risk factor develops symptoms, we want to make sure that they get the necessary care that they need to get properly evaluated, because they might be sick for a variety of different reasons, not just coronavirus, but also for other reasons.

Suppose somebody is ill but not seriously. They have a mild condition and they've tested positive for COVID-19. Then what happens?

The good news about this virus is that it seems like a lot of the illness caused by the virus in most people is actually pretty mild, though unfortunately, some people do face more severe consequences, including pneumonia and even death. And the people who tend to have the severe consequences of the disease tend to be people who are in older age groups or people with chronic comorbidities.

But at the same time, because this disease is mild, it might actually be contributing to more widespread transmission of this virus, because people who are mildly symptomatic might not feel so sick that they have to go to a hospital and then they might end up interacting with other people and exposing them. And for that reason, we definitely take isolation very seriously whenever we confirm a case or even if there's a person as a suspected case, they should be isolated, quickly. And sometimes that will happen in a hospital setting. Sometimes they're not so sick that they don't need to go to the hospital.

Is there a point when there are so many cases, that you essentially stop tracing contacts because the virus is so prevalent in the community, the way that you don't track every flu case. In other words, do you just give up essentially at some point?

Well, it's certainly not giving up. We do a lot of forward planning to think about where's the infection going, where the epidemiology of the infection is globally and what can we expect from New York City. And that planning is really important. And part of that before planning, is planning for the possibility of sustained community transmission of this virus in New York City.

I think every New Yorker needs to be prepared and realize that we are probably going to see more cases of coronavirus in New York City. This is understandably scary for many of us because this is a new virus. There's a lot we don't know about it. And we should have a healthy level of fear because that helps us to do the right things, to stay safe. But at the same time, you know, what I'm trying to say is that we should expect to see additional cases, possibly even transmission in the community. And if we were to see a lot of transmission in the community, certainly our approach would change, because if there's a lot of transmission in the community, that means everyone is at risk.

We use CDC information to help us guide our investigations and then we tailor our responses accordingly. And so it really depends on the number of contacts. But again, if it gets to a place where there's a lot of cases in your city, at some point, yes, it might become just not feasible to track every individual contact because so many people have been exposed, then everyone essentially becomes at risk. But we're not there yet.

Ok, one silly question and then I'll let you go. Have you watched Contagion? Are you afraid of dying like Kate Winslet's character did?

So I watched Contagion the night that the movie got released. As a teenager I watched the movie Outbreak, and I decided that I wanted to chase diseases with with my life. And I'm very lucky that I get to do the work that I do. My dad actually had smallpox as a kid and that also obviously inspired my choice of career. And, you know, I think the people who are the real heroes in any response are the many people [like] frontline clinical workers who are really the ones doing so much hard work and taking care of patients and keeping people safe and healthy. [They] are also, unfortunately, at risk because they see patients who might have an infectious disease. So it's really important that we let health care workers know the information that they need so that they can stay healthy.

This interview has been condensed and edited for clarity.