Dr. Lynn D’Andrea knew something was amiss when three teenagers with similar mysterious lung injuries came into the Children’s Hospital of Wisconsin one after another, gasping for air.

As the only pulmonologist on duty that July 4th week, she noticed those cases followed on the heels of another teen who had a noninfectious condition with matching symptoms.

“ ‘We need to be thinking about something else,’ ” she told Dr. Michael Meyer, medical director of the Pediatric Intensive Care Unit, as he later recounted. That “thinking about something else” led to the discovery of nearly 900 probable vaping-related injury cases in 48 states and a U.S. territory, with other cases reported in Canada. At least 18 people have died, including in Minnesota.

The epidemic has prompted outrage about federal oversight, but there is also a local public health success story to be told. It’s a tale of teamwork, communication and long-serving public health officials tapping into their networks in an era of limited public health funding.

It’s surprising in some ways that Wisconsin became ground zero for uncovering the link. The state has ranked near the bottom nationwide for per-person spending on public health until a boost of $588 million more was greenlighted for the next two years. Wisconsin is also home to Juul vaping pod manufacturing sites and Sen. Ron Johnson, R-Wis., credits his win to vaping advocates.

And yet the state’s officials discovered the outbreak. “I don’t think anyone could have anticipated how wide-reaching this problem has become,” D’Andrea said.

Although isolated cases were spotted as early as 2015, a wave of cases began popping up across the country starting in April. Patients, many of them teens, complained of shortness of breath, weight loss, fatigue and gastrointestinal issues. They often had acute respiratory distress syndrome, a lung injury from an unknown cause.

Doctors used extensive patient histories to piece together the missing link among that cluster: vaping.

This is no easy feat working with teenagers who may not want to admit to vaping in front of their parents. But D’Andrea said the patients’ openness helped make the discovery possible. “They were part of the ‘team,’ ” she said.

After discussing the cases with Meyer and other colleagues, D’Andrea called Dr. Michael Gutzeit, the hospital’s chief medical officer, on July 8. That call raised the warning to the local health department, then to the state health department and eventually to the Centers for Disease Control and Prevention — effectively putting the health crisis on the nation’s radar.

“It’s incredible that they saw this,” said Dr. Jeffrey Gotts, a pulmonologist in California. “As front-line clinicians, there are very few things that we would report to public health authorities in the ICU.”

Because the four patients at Children’s Hospital of Wisconsin were from Waukesha County, specialists from the hospital called the local health department. Waukesha’s public health officer, Ben Jones, reached out to the state’s respiratory disease epidemiologist, Thomas Haupt.

Haupt was alarmed. He went to work notifying fellow public health officials across state lines. “Communication is always the biggest asset you’ve got as far as any disease investigation,” he said.

In the meantime, the state health department and Children’s Hospital coordinated a press announcement and clinicians’ alert on July 25. Within days, a clinician in Illinois called the Wisconsin state health department worried that a patient there might have the same condition.

In San Francisco, Dr. Elizabeth Gibb saw a patient whose mom had seen the news out of Wisconsin and asked whether it might be connected to her teenager.

Following the Illinois case — and one month since that call from D’Andrea to Gutzeit — the Wisconsin health department sent an alert to all state health departments on the Epidemic Information Exchange network run by the CDC. From there, it started to snowball.

As the caseload has quintupled, much still remains unknown about the illness. Still, Haupt said he’s incredibly proud of the work the officials in Wisconsin did. He believes their notification may have helped save lives.

“That’s the way public health is supposed to work,” he said. “And trust me, it doesn’t always work that way.”