Ebola’s Disease Detectives Race to Track Others Exposed

The day Thomas Eric Duncan’s Ebola infection was confirmed, 10 federal disease detectives -- redirected from around the globe -- raced to the city of Dallas to help trace Duncan’s contacts in the community.

They weren’t armed with complex scientific equipment or full-body protection. Rather, they carried simple thermometers, gloves and BlackBerry mobile telephones, said Dave Daigle, a team member. Their job: Interview and then monitor a widening circle of people, starting with those who were in direct contact with Duncan and including anyone who interacted with that group since they met up with Duncan.

Working with Dallas-area health officials, the 10-man team has identified as many as 100 people who could potentially be infected. On a daily basis, they will monitor this group for 21 days primarily by regularly checking for a high temperature, a key early identifier for the disease.

“It’s a shoe-leather job,” Daigle, who recently worked in Nigeria, said by telephone. “Not terribly sexy.”

As soon as the federal team arrived, it joined with a second 10-person group from the county health department that had begun tracing Duncan’s contacts even before his Ebola was confirmed, said Erikka Neroes, a spokeswoman for Dallas County Health & Human Services. The two teams are now working together to quickly isolate a disease that has raced through three West African nations since early in the year, infecting almost 8,000 people and killing about half.

‘Casual’ Interviews

The initial contact interviews by the federal team are “casual,” designed to calm people’s fears as detectives gather information about the hourly activities and contacts of the people they are talking with, according to Daigle. No scary-looking white plastic protective suits are worn, helping to keep conversations as low-key as possible, he said.

The team, made up of staffers from the U.S Centers for Disease Control and Prevention, includes three “pretty senior epidemiologists,” a public health adviser, a communications specialist and five members of the CDC’s Epidemic Intelligence Service unit. Called the “disease detectives” by Daigle, the EIS comprises well-trained epidemiologists who’ve undergone an elite two-year program, Daigle said.

Collaboration between the local officials, who know the area well, and the federal workers, who have detailed disease expertise, is standard procedure for significant outbreaks, said Jason McDonald, a CDC spokesman.

Command Center

The local group is working out of an incident command center in the heart of the city of Dallas to manage the effort, said Neroes. While the CDC staff are based in the hospital where Duncan is located, Daigle said there is almost constant contact between the two teams.

“The operation center is fielding calls and sending out information through multiple channels,” making sure each tip it receives about possible contacts is followed up on and information from the field is filtered down to all the necessary entities, Neroes said.

“There is no such thing anymore of 8 to 5” for the either group, she said. “People are stepping away at varying times to get some sleep -- 2 hours here, 1 hour there.”

Daigle recently returned from Nigeria and planned to embark on leave on Monday to visit his mother. Before he could do that, he was called at about 1 p.m. on Tuesday, the time the Texas state health department said the patient tested positive for Ebola, and told to pack. By 3 p.m. he was on his way to Dallas.

Now, “I’m not sure what day it is,” Daigle said.

Infected Person

The interview process is designed to be “casual” but complete, the CDC’s McDonald said. The first step is interviewing the infected patient. If they determine the patient has close contact with another person, that individual will be monitored by the CDC team for 21 days.

Thomas Frieden, the CDC chief, wrote on Twitter yesterday that the U.S. health agency won’t consider the threat in Dallas over for at least 42 days. “We are taking no chances, leaving no stone unturned, until 100% sure Ebola virus contained,” Frieden tweeted.

The Dallas disease trackers first mapped out in concentric rings those who Duncan touched, kissed, or hugged. Then, they turned their attention to anyone the initial group may have been in contact with.

“In most cases, people are willing to cooperate with the agency,” the CDC’s McDonald said, “I’ve heard of rare instances where you couldn’t find someone. But for the most part you can get ahold of them.”

Enough Manpower

The two teams should have more than enough manpower to reach and follow up all the contacts that Duncan may have had in the days he was contagious, said William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center, who is not directly involved in the effort.

Contact tracing is a core skill that big-city public health departments usually excel at, according to Schaffner. It is basic “blocking and tackling” for the municipal public health arena, he said.

“You walk people through their memories,” Schaffner said “You give them a chance to reflect on the days in question” in interview that usually takes in the range of 15 minutes to a half hour in some cases.

In Duncan’s case, teams on the ground probably traced his actions from the earliest possible moment he may have had symptoms. In addition to people living in the apartment where Duncan was staying, hospital employees who had any contact with Duncan will also be watched closely, particularly those who might have taken care of him with fewer precautions during his first visit to the hospital, when he was released with the presumption he had a routine virus, said Schaffner.

ER List

“Everyone who touched that patient at the hospital in the ER will be on that list,” he said.

High risk patients, such as the four family members with whom Duncan was staying and who are now quarantined in their apartment home, are not allowed to have visitors and are checked by the investigators twice a day for fever or other Ebola symptoms, the CDC’s Daigle said.

Low risk patients, which in this case include schoolchildren and community members, are checked in person once a day and also called. If the contacts are unreachable, or they refuse to participate, state and county authorities have the legal authority to confine them to their homes.

‘Zero Risk’

Classmates at the schools that kids from Duncan’s apartment attended “have close to zero risk” of getting Ebola, because the disease does not spread from people who are not sick yet, Schaffner said.

Daniel Bausch, a professor of tropical medicine at Tulane University, said that Duncan was likely not very contagious when he went to the hospital the first time and was discharged because he didn’t appear to be all that sick.

That’s because the contagiousness of an Ebola patient is proportional to how sick the patient is and how much virus he has in his system, he said.

“Most transmission occurs from very sick patients late in the course of the disease” when patients have more virus in their system and are vomiting or have diarrhea, he said.

“When they are in early stages of disease and they just have fever and a headache they have a low level of virus, so they are unlikely to transmit it,” he said.

In Duncan’s case the number of contacts at higher risk of the disease because they were near him when he was quite sick are likely to be few in number, Bausch said.

“There may be a few people who had close contact with him who potentially could have gotten exposed to bodily fluids,” he said. “The number of high risk contacts from this sort of event is actually very low.”

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