You may have heard about “contact tracing” — the painstaking process that the Centers for Disease Control and Prevention is using to find everyone who has come in direct contact with the Ebola patient in Dallas.
From my two-year experience as a CDC disease detective, I can say contact tracing is both a science and an art.
The science part is easy. You have a patient with an infectious disease, and you want to track down every person he or she had contact with while infectious.
The art part is harder — and it’s the part they don’t write about in textbooks. That part deals with how to get people to talk to you.
One day in March 2013, I found myself in the parking lot of a grocery store on an American Indian reservation on the Arizona-New Mexico state line, trying to get a homeless man to talk to me.
I was with four others, part of an outbreak investigation team trying to stop the spread of a flesh-eating bacterial infection known as invasive group A streptococcal disease.
By the time we arrived, three people were dead.
By the time we left two weeks later, 11 people had fallen ill.
On the team, three of us were disease detectives and two were tribal public health workers with the Navajo Nation who would help us navigate local etiquette and language. When we arrived, the community was tense and skeptical about who we were and what we were doing.
Del, a tribal public health worker who was sharp and enthusiastic, stood next to me in the grocery store parking lot and said, “That’s the man we need to talk to.”
The man was disheveled and dusty, swaying slightly in the heat and clutching a Styrofoam cup filled with something frothy.
“That’s what they call ocean,” Del said, referring to the effervescent fluid in the cup. Ocean was a cocktail of hairspray and water, a cheap way to get drunk on the reservation, where alcohol was forbidden.
“Can you give me a dollar?” the man asked as we approached.
“He wants it to buy hairspray,” Del said. Moments earlier, he had walked us through the toiletries aisle in the grocery store where bottles of hairspray were kept behind glass, in a padlocked cabinet.
Other tribal members who had been sickened with the flesh-eating bacteria said they had contact with a woman named Marcy days before their illness. (Marcy’s name has been changed to protect her privacy.)
They told us Marcy had a rash — one of the early signs of the bacterial infection that, for some people, doesn’t progress into anything serious.
We suspected she had passed the bacteria on to others who became a lot more sick than she did. Many people are healthy carriers of this bacteria, and poverty, poor hygiene and limited access to water can make people more prone to serious illness.
Marcy was our “Patient Zero.”
We were told that a man we would find in the parking lot, drinking ocean in the daylight, could lead us to Marcy.
But the man didn’t want to talk. He said he didn’t know Marcy. He said that he didn’t know what outbreak we were talking about. We retreated and huddled, looking for a different strategy.
This time, Del approached on his own. He used a friendly tone in Navajo. He returned to us a few minutes later, smiling.
“Marcy hangs out in the parking lot in the evenings,” Del said. “We have to come back.”
People’s perception of disease detectives means everything in contact tracing. Not only did Del speak Navajo, but he approached in a casual way that didn’t indicate that he was part of a federal team investigating a deadly outbreak.
He just made conversation. He did tell the man how important it was that we find Marcy and that she get medical treatment.
We returned to the Indian Health Service hospital that was our incident command center, crowding into a room with a long table cluttered with patient charts, laptops and the bright green notebooks that the CDC issues each disease detective for every new outbreak.
For long days, we combed through patient records, looking for any clues as to how this outbreak was spreading.
We needed to track down anyone who’d had contact with Marcy. But we also had to find everyone who’d had contact with the 11 patients, including the three who had died, while they were infectious.
Sometimes, just locating the house of a potential contact was difficult. The medical charts would list addresses as “the house with the blue roof that is half a mile down from Milepost 22,” or “the trailer next to the white house, opposite the canyon.”
We got to know the reservation well. The nurses who worked with us always drove us from the hospital to the homes of potential contacts. We would gather at the front door and try to look professional and friendly while asking questions that were on our contact tracing questionnaire. “Have you had a rash? What about skin wounds?”
I recall one woman ignoring the questions and saying, “My neighbor’s friend died from this disease. How do I stop my kids from getting it?”
I answered: “Well, it’s quite easy, actually. Just wash your hands frequently and make sure the kids practice good hand hygiene.”
But there was a problem. The woman said her house — and many others on the reservation — didn’t have running water.
We learned that many homes lacked flushing toilets and that some people managed their own water systems, driving for hours to fill up huge tanks that sat outside their houses. One of the tribal health workers on our team told me that he drove his truck to fill up a water tank.
“When the water runs out, it’s a pain,” he explained. The lack of water, which had an impact on hygiene, was partly the cause of this epidemic.
We returned to the grocery store parking lot on three nights, each time finding different homeless people but not our Patient Zero.
Then one night, after an especially grueling day of contact tracing, we found Marcy.
She was in the middle of a group of mostly homeless people, talking in the parking lot. She was the center of attention, which made sense — a lot of people had come into close contact with her while she was infectious.
“Are you Marcy?” one team member asked.
The woman smiled and said, “Yes.”
As we walked across the parking lot with Marcy, we explained the outbreak. We asked her if she’d had a rash. She said that she had but brushed it off as nothing — an annoyance that healed with a little lotion.
Marcy told us more about her life. She was chatty and happy, which made our job easier. She offered us information that helped us fit the pieces of the outbreak puzzle together.
Marcy said that because she was homeless, she would seek different places to sleep every night. On a good night, a friend would offer a couch or a bed. Often Marcy slept alongside them, the perfect way for the bacteria to pass from one person to another.
With that information in hand, we continued our contact tracing on the reservation.
Slowly, we filled our office whiteboard with names.
By the end of our investigation, we had tracked down 58 contacts of infectious patients and built trust with the community.
And the outbreak ground to a halt as the chain of transmission was broken.
Dr. Seema Yasmin, a former epidemiologist with the Centers for Disease Control and Prevention, is a physician and a professor at the University of Texas at Dallas. Follow her on Twitter at @DoctorYasmin.
