As she was leashing up Rosa, the phone on her belt vibrated. She brought it to her ear. “Lina, it’s Nelson Amar,” her boss said in his usual crisp voice.

She straightened. “Oh, Nelson, I was going to call you in the morning.” She glanced at her watch and calculated that being 10:15 in Seattle meant it was after midnight in Atlanta. “I thought it was too late now.”

“‘Late’ is part of the job description at EIS, Lina,” Amar said, and Lopez wondered if he meant to be condescending. “I wanted to talk to you about this resistant group-A strep.”

“You’ve heard?” Lopez said. “I only got the results a couple of hours ago.”

“I heard yesterday,” Amar said.

“Yesterday?” her voice squeaked, causing her to flush. “I don’t understand … .”

“Dr. Graham Kilburn called me,” Amar said, his voice taking on an impatient edge. “They’ve known for days. In fact, Kilburn had already been in touch with the WHO.”

The conversation kept getting murkier for Lopez. “I don’t know a Dr. Kilburn.”

Papers rattled in the background. “An infectious disease specialist at … St. Michael’s Hospital.”

“St. Michael’s?” Then it hit her. “Nelson, you’re not talking about Seattle, are you?”

“Kilburn works in Vancouver, Canada. You’re the closest EIS officer I have in the region.” Amar’s voice assumed a suspicious edge. “Wait a minute. If you didn’t know about the Vancouver cases, how did you know about the resistant G.A.S.?”

Lopez’s mouth went dry. She dropped Rosa’s leash. “We have at least two cases in Seattle,” she said quietly.

“In Seattle?” There was a long pause. “Just when were you planning to tell me?” he said gravely.

“In the morning,” she mumbled, too preoccupied to care about his reprimand.

“Lina, tell me about the Seattle cases—now.”

Lopez told Amar what she knew of the dead HIV-positive addict with pneumonia, Tonya Jackson, and the second case, Harry Wales, with the necrotizing fasciitis. “I’ve only known for less than three hours, but we’ve put the hospital on the strictest infection-control alert. And we’ve issued a warning throughout King County to report any case of streptococcal infection. I’m just about to draft an urgent e-mail memo for all public health officials and physicians in the region.”

Lopez stopped and waited for Amar to elaborate on the Vancouver cases, but he remained silent. Amar had a reputation at the CDC for tightlipped evasiveness even with members of his own team, but she was determined not to be left out of the loop. “Nelson, what’s going on in Vancouver?”

“There have been three cases with similar lab results to yours,” he paused, as if weighing how much more to share. “A previously healthy man died of pneumonia. Another woman is being treated—if that’s the right word—for a necrotizing fasciitis of her arm.”

“And the source?” Lopez pressed.