Unless you know an epidemiologist or are one yourself, those “disease detectives” might not have occupied a very large portion of your brain. Last year, that is. Now, with the coronavirus pandemic at the top of mind—and at the top of so many headlines—there’s a good chance you’re at least aware that epidemiologists study diseases.

To be more specific, the Centers for Disease Control and Prevention (CDC) defines epidemiology as “the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.” So what exactly does this mean? Mental Floss spoke with a few epidemiologists to shed light on what they do, how they do it, and which germ-friendly foods they avoid at the buffet.

1. People often mistake epidemiologists for skin doctors.

Since the word epidemiologist sounds like it might have something to do with epidermis (the outer layer of skin), people often think epidemiology is some offshoot of dermatology. At least, until the coronavirus pandemic.

“Prior to that, no one knew what I did. Everyone was like ‘Oh you’re an epidemiologist—do you work with skin?’” Sarah Perramant, an epidemiologist at the Passaic County Department of Health Services in New Jersey, tells Mental Floss. “I would be rich if I had a dollar for every time I got asked if I work with dermatologists.”

2. Epidemiologists don’t discover a new disease every day.

Though some epidemiologists do look for unknown diseases—certain zoonotic epidemiologists, for example, surveil wildlife for animal pathogens that might jump to humans—most are dealing with diseases that we’re already familiar with. So what do they do every day? It varies … a lot.

Epidemiologists who work at academic or research institutions undertake research projects that help determine how a disease spreads, which behaviors put you at risk for it, and other unknowns about anything from common colds to cancer. But it’s not just about devising experiments and studying patient data.

“I like to tell my friends and family that my job is about four different jobs in one,” Dr. Lauren McCullough, an assistant professor in the department of epidemiology at Emory University’s Rollins School of Public Health, tells Mental Floss.

Writing, she says, is “the most important part.” It includes requesting grants, devising lectures and assignments, grading her students’ work, writing about her research, and more. She also sits on admissions committees, reviews other epidemiologists’ studies, and oversees the many people—project managers, data analysts, technicians, trainees, etc.—working on her own research projects.

Those who work in the public health sphere are often monitoring local outbreaks of diseases like the flu, Lyme disease, salmonellosis, measles, and more. If you test positive for a nationally notifiable disease (any of about 120 diseases that could cause a public health issue), the CDC or your state health department sends your electronic lab report to the epidemiologist in your area, who’s responsible for contacting you, finding out how you got sick, and telling local officials what steps to take in order to prevent it from causing an outbreak.

3. Epidemiologists have to make some uncomfortable phone calls.

At least the person on the other end can't see your expression of consternation. Andrea Piacquadio, Pexels

Epidemiologists sometimes have to ask pretty personal questions about drug use and sexual activity when trying to figure out how someone got infected, and not everyone is happy to answer them. “I’ve gotten hung up on many a time,” Dr. Krys Johnson, an assistant professor in Temple University’s department of epidemiology and biostatistics, tells Mental Floss.

Some simply aren’t willing to accept that they might have been exposed to a disease without knowing it. After several employees at a certain company tested positive for COVID-19, for example, Perramant started calling the rest of the workers to tell them to go into quarantine; this way, she could prevent sick people who weren't yet showing symptoms from spreading the disease without knowing it. But not everybody was open to her advice. “They would just swear up and down, ‘I haven’t been in touch with anybody who’s positive, please don’t call me again,’” Perramant says.

But there are plenty of cooperative people, too, especially victims of foodborne or diarrheal illnesses. “They really want to know where they got sick because they’re so miserable that they never, ever want to deal with that again,” Johnson explains. Parents of sick kids are also generally forthcoming, since they want to keep their kids healthy in the future. And then there are those who don’t have any problem spilling their secrets to a stranger.

“There was one woman who was very memorable,” Johnson says. “I called her about her Hepatitis C, and she was like, ‘Oh, honey, I did drugs back in the ’80s. That’s where I got my Hepatitis C. I pop positive every time!’”

4. Epidemiologists deal with a lot of rejection.

Public health epidemiologists have to learn to just shrug off all the rude tones and dial tones, and epidemiologists in academic settings need thick skin for different reasons.

“There’s just a lot of rejection,” McCullough says. “‘That idea isn’t good enough; this paper isn’t good enough; you’re not good enough.’ That is just a resounding thing. There’s a high bar for science; there’s a high bar for federal funding; and it takes a lot to cross that bar. So in the academic setting at these top-tier institutions, you really just have to have a thick skin.”

5. Just because epidemiologists' guidelines change doesn't mean they're wrong.

Sometimes, McCullough explains, the story of a disease can change over the course of one study. When you look at the first 100 people in a 10,000-person study, you’ll see one story emerge. By the time you’ve seen 1000 people, that story looks different. And after you’ve seen the data from all 10,000 people, the original story might not be accurate at all.

Usually, epidemiologists can complete the whole study of a disease and draw conclusions without the world clamoring for half-baked answers. But with a brand-new, highly infectious disease like COVID-19, epidemiologists don’t have that luxury. As they’ve learned more about how the pathogens spread, how long they can survive on surfaces, and other factors, they’ve changed their recommendations for safety precautions. Everyone else in the world of epidemiology expected this to happen, but the general public did not.

“If we say something this week that contradicts what we said last week, it’s not that we were wrong,” Johnson says. “It’s that we learned something between those two time points.”

6. Being an epidemiologist would be easier if people kept better track of their behavior.

Often, people omit vital information about how they got exposed to an illness because they just don’t remember all the details. You could easily recall devouring a few slices of the decadent chocolate cake your mom baked for your birthday last Friday, but you might not be able to name every bite of food you ate on a random Thursday three weeks ago.

“People aren’t telling us the whole truth, but it’s not that they’re being intentionally obtuse,” Johnson explains. “With recall bias, unless there’s a reason for us to really remember, we’re not going to remember everything we actually ate.”

This has made it especially difficult to trace an aerosolized disease like COVID-19.

“All my friends going into the Fourth of July were like, ‘Should we have a get-together?’” Perramant says. “And I said, ‘You can have people over, but you better take an attendance list. You better have a little spreadsheet on Google Drive that has every person’s name and their phone number, so that when one person tests positive and gets sick this week, when I call you, you will be able to give me that information like that.’”

7. Epidemiologists have reason to be wary of buffets, cruise ships, mayonnaise, and cubed ham.

It's all fun and games until someone eats warm egg salad. Tim Meyer, Unsplash

Infectious disease epidemiologists may have accepted that germs are a part of life, but they also know where those germs like to congregate.

“I don’t go to buffets, I have never been on a cruise ship and I don’t intend to, I’m super conscientious when I fly,” Johnson says. “And I’m really aware of whenever mayonnaise-based things are put out at family functions. If you’re ever at a potluck and people come down sick, the first thing people say [they ate] is potato salad or egg salad, because mayonnaise can spoil so quickly.”

“[Cubed ham] is one particular microbe’s very favorite thing to multiply on, so if you’re gonna have ham, make it a whole ham,” she says.

8. Teaching people is a really rewarding part of being an epidemiologist.

In addition to actually leading lectures in the classroom, academic epidemiologists also work extremely closely with their students on research projects; McCullough estimates that she’s in contact with hers at least once a day when they’re collaborating on a study.

“To work with someone so closely, and to watch them progress as a scientist and as a person, and then to have to let them go and send them out into the world, I find that very rewarding,” McCullough says of her trainees. “As a scientist in an academic institution, there’s not a whole lot of immediate gratification. Our papers get rejected, our grants don’t get funded, but the trainees are always a source of immediate gratification for me, so I hold them close to my heart.”

Epidemiologists in other spheres have teaching opportunities, too. When a community experiences a disease outbreak, public health epidemiologists like Perramant are responsible for helping the general public understand what they can do to prevent the spread.

“I like to teach kids about infectious disease and infection prevention for what’s relevant to them. We’ve had a couple of large outbreaks at summer camps, and last summer I put together a training for camp counselors,” Perramant says. “That’s always a part of my job that I really love.”

9. Epidemiologists have a unique understanding of racial disparities.

At this point, it's exceptionally clear that COVID-19 is disproportionately affecting people of color in the U.S. They're more likely to be exposed to it, they have less access to testing, and the preexisting conditions that place them at a higher risk can be the result of systemic racism. When these trends started to become apparent, McCullough got flooded with phone calls asking why. Her answer? This isn’t new. As she’s seen in her work as a breast cancer researcher, Black women are more likely to die of that disease than their white counterparts, and similar health disparities exist across the board.

McCullough explains that the general public is finally realizing what epidemiologists already knew: That poor disease outcomes in minority, low-income, and rural populations aren’t because of anything those people are doing on an individual level. Instead, it’s a result of systemic issues that keep them from leading financially comfortable, healthy lifestyles with access to healthcare and other resources.

“It’s not just COVID—it’s almost every single chronic and infection ailment that’s out there,” McCullough explains. “So this is a real opportunity for people to step back and take an assessment of where we are in terms of our healthcare system, and what we’re doing so that everybody has equitable outcomes. Because people shouldn’t die just because they live in a rural area, or just because they’re poor, or just because they’re Black or Hispanic.”

10. They've had to deal with a lot of “armchair epidemiologists” lately.

Until this year, epidemiologists had to suffer through people mistaking them for dermatologists. Now, during the coronavirus pandemic, people finally know at least a little about their jobs. In fact, people are so confident in their newfound epidemiological knowledge that many are fancying themselves experts on the subject.

“At the beginning of 2020, there were like 500 epidemiologists, and now there are about 5 million. Everybody thinks they’re an epidemiologist,” McCullough says. “There’s a science to it, and it’s a science that requires training. We went to school for a really long time to be doctorally trained epidemiologists.”

It’s not just about advanced degrees, either. Beyond that, you need years of firsthand experience to grasp all the nuances of understanding methods, interpreting data, translating your findings into recommendations for the general public, and so much more. In short, you can’t just decide you’re an epidemiologist.

Perramant has her own analogy for the recent influx of self-proclaimed epidemiologists: “It’s like armchair psychology. Poolside epidemiology now is a thing.”