With any infectious disease, finding out how the pathogen spreads and who has been exposed is a crucial part of the health response. Across the country, as the coronavirus outbreak grows, disease detectives are on those front lines, investigating the threat, tracking down those who may have come into contact with a COVID-19 infected person, and collecting as much data on this novel illness as possible. And before they go out into the field, these disease detectives are trained at the CDC’s Epidemic Intelligence Service Program.
There are currently 130 EIS officers in the two-year service training program, which recruits physicians, nurses, veterinarians, and doctoral-level scientists, and many of those are out in the field right now, working with state and local health departments to curb the spread, and better understand, the novel coronavirus. (EIS has trained more than 3,600 disease detectives since 1951.) In South Korea, this kind of “contact tracing,” along with mass testing, has helped contain the disease. In the U.S, though COVID-19 is a priority for our disease detectives, now that we’ve hit a point of rapid community spread, this kind of intervention can’t fully contain the coronavirus. That’s why cities are taking steps toward mass quarantine. But still, disease detectives are important to learning as much as we can about this new illness, and that information could help officials better contain and treat COVID-19.
Once in the field, a disease detective’s work always starts with an invitation from a state or local health department, or in some instances an international partner, says Eric Pevzner, chief of the CDC’s EIS Program. “We don’t go anywhere without an invitation,” he says. “Sometimes it can be when there’s a single case, if it’s something very novel and new, or sometimes it can be when there’s a cluster of cases of a known disease, but we’re unsure why people are getting it.”
When dealing with something that’s infectious, a lot of the work for a disease detective lies in trying to determine how transmissible that disease is and who else may have been exposed. “You can ask someone if they know the names of the people they’ve been spending time with, and you follow up and you can have a name-based investigation,” Pevzner says. “When it’s people that they may not know by name, then oftentimes you need to do a location-based investigation, so you try to determine where they’ve been spending time, and then you look at the best available data sources to determine who else has been in that shared space.”
Whenever you have an infectious disease, and you have a large public gathering, and you don’t even know how many people in that space have an infection, it definitely makes it much harder for our disease detectives.”
Sometimes this work is easy; disease detectives focused on who that person has spent the most time around, like people in their home or their workplace. If a disease detective is investigating the spread of COVID-19 from someone who has been on a plane, they can look at the flight manifest to find out who else was a passenger (problems getting this information to the CDC seems to have slowed down some tracking in the COVID-19 hunt). Sometimes it’s harder, like if an infected person recently ate at a restaurant. In that case, disease detectives may put out an announcement to find who else was at the restaurant at the same time, work with local public health experts, or get creative with some innovative investigating techniques.
“Years ago, we had an officer that, during influenza time, was able to conduct some advanced analytics and look at sales of certain products that would indicate whether someone was likely to be infected and be looking for medication,” Pevzner says. Another disease detective once looked at how air moves around a cruise ship to better determine who may have been infected by a pathogen passing through the air ducts.
Part of that innovation comes from the fact that the CDC’s disease detectives come from a variety of backgrounds. “Having a breadth of expertise in the program, it allows them to call on their other training and come up with ideas that we might not think of with strictly a public health training or background,” Pevzner says. “We have people that come in that are trained as microbiologists, we have people with backgrounds in anthropology. We have other people with different degrees in laboratory science. We have people that started from the ground at NGOs. We have people that have worked in the private sector and people with backgrounds in business. They have medical and public health training, but not all of them have had a linear path to public health.”
As the coronavirus outbreak has worsened across the country, officials have taken steps to try to reduce the chance of COVID-19 community spread, which is when there is no longer an isolated incident of infection, but multiple people who are moving around—many undiagnosed—in a community, leading to ongoing transmission. “Whenever you have an infectious disease, and you have a large public gathering, and you don’t even know how many people in that space have an infection, it definitely makes it much harder for our disease detectives,” Pevzner says. “It makes it much more difficult to follow up and have a complete investigation.”
Each day that disease detectives are on their COVID-19 cases, they learn more about the disease: how contagious it is, how it spreads, the severity of the illness, what groups are most likely to be affected. “Similar to other emerging pathogens, we’re learning something new everyday,” Pevzner says. “And that makes it difficult for everyone.” Disease detectives work with state and local health partners to tease out this information by determining when someone got sick, how many other people have been exposed, and following up with those people to see how many of them became ill.
COVID-19 is the priority of the EIS program, but disease detectives in general are always working on other tasks. A few disease detectives are deployed on the global response to ebola and others are contributing to the CDC’s polio eradication efforts. Prior to the coronavirus outbreak, many EIS officers had been on deployments focused on EVALI, the lung disease associated with vaping and electronic cigarette use, and before that, the opioid epidemic. “These groups of individuals have been repeatedly stepping forward,” Pevzner says, “to deploy for whatever priority and threat is facing the public health of American people.”