But contact lists grew quickly. With each passing hour, a pathogen would reach more and more people. Time was of the essence; in most cases, the first few days of an outbreak determined everything after.

On a pad, Peyton had written the names of the two Americans, Steven Cobb and Lucas Turner, as well as the British patient, Andrew Blair. Between them, she had drawn a large X. The X was the variable, the unknown—what she needed to find. At some point, the British man had interacted with one or both of the Americans. Either that, or all three had a common contact—someone still out there, continuing to spread the disease. It was imperative that she find out where each of them had been and whom they had interacted with. The travel log could be the key to doing that.

If Peyton and her team did their job correctly, they’d end up with a contact tree that eventually had a root contact: the first person to contract the disease, often called patient zero or the index case.

That was the on-the-ground detective work: tracing the pathogen to its origin, containing every person it had touched, and either treating the patients or simply waiting for the outbreak to burn itself out.

But even with the video travel log, Peyton and her team were going to need a lot of help in Kenya.

She picked up her office phone and called Joseph Ruto, head of the CDC’s office in Kenya. Ruto was just finishing a late lunch in Nairobi, which was eight hours ahead of Atlanta.

She briefed him on their plans, with the caveat that they might change after the morning conference. The man struck her as competent and focused, and she counted that as a very good sign.

It was just before six a.m. when she hung up. She had been waiting to make the next call; she wanted her people to get as much rest as possible. Sleep might be hard to come by in the coming days.

She dialed the EOC’s head of watch and requested they contact all of the Epidemiology Intelligence Service agents.

“All of them?” the watch officer asked.

“Everyone assigned to CDC HQ. Instruct them to be in the building by seven a.m. for a pre-conference briefing. They need to come packed and prepared to leave in a few hours. If they’re deployed, they’ll be working either in Nairobi or in the field in rural Kenya. Instruct them to plan accordingly.”

“Understood, Dr. Shaw.”

The EIS program was a two-year fellowship established at the CDC in 1951. It had begun as a Cold War initiative focused on bioterror. Today it was one of the most prestigious and sought-after fellowships in applied epidemiology, known for producing the world’s best disease detectives. Candidates applying to the program needed to be either a physician with at least a year of clinical experience, a veterinarian, a PhD-level scientist with a background in public health, or a health care professional with at least a masters degree in public health. There were currently 160 EIS officers, seventy percent of whom were women.