Former CDC chief Rochelle Walensky nailed the diagnosis. But the standing ovation from a roomful of doctors, medical students, and other members of the Massachusetts General Hospital community at a special event held recently was as much about where she’d been and what she’d learned about pandemics as her diagnostic acumen.

In 2021, amidst the COVID-19 outbreak, Walensky left appointments at MGH and Harvard Medical School to lead the Centers for Disease Control and Prevention, giving her an influential voice in U.S. pandemic policy, even as she made herself a target for people angry about those policies. After two years, during which she received enough death threats to warrant a full-time security detail, Walensky left the post in July and returned to Boston.

Today a lecturer at Harvard Law School, executive fellow at Harvard Business School, and Women and Public Policy Program senior fellow at Harvard Kennedy School, Walensky said in an interview that she’s taking time to consider what comes next for her. In the meantime, she’s enjoying teaching at the intersection of law and health care. And it’s clear from the MGH event marking the 100th anniversary of a legendary case-study feature in the New England Journal of Medicine that she hasn’t lost any chops as a physician.

“We have tenaciously hung onto what I think of as a marvelous tradition of case-based teaching,” said Eric Rosenberg, who edits “Case Records of the Massachusetts General Hospital” for the NEJM. “To my knowledge this is the oldest case-based teaching exercise in modern medicine. Since Dr. Cabot first started publishing in 1923, the MGH, in collaboration with the New England Journal of Medicine, has now published 7,062 cases.”

To mark the anniversary, a team of physicians re-presented the very first case, which involved a 24-year-old student who came to MGH in March 1923 complaining of pain and breathing problems. The student rapidly worsened and died within a few days.

Walensky, who was head of MGH’s Division of Infectious Diseases before leaving for the CDC, walked the audience through her assessment of the case and diagnosis. The student likely had influenza — 1923 was just a few years after the 1918 Spanish flu outbreak — complicated by pneumonia caused by a bacterial infection, she said.

The diagnosis, however, was just the kickoff for a broader talk about progress fighting influenza since 1923. Walensky discussed the nation’s handling of influenza epidemics in 1957, 1968, and 2009, as well as the COVID-19 pandemic. The news is both good and bad. While medical science and technology have vastly improved surveillance capacity, diagnostic tools, and the treatments at physicians’ disposal, politics is still getting in the way.

“We’ve had remarkable progress in science since 1918,” Walensky said. “What’s been stagnant since 1918 is political will.”

In that year, Walensky said, the so-called “Spanish flu” was first diagnosed in a U.S. Army cook in Kansas and spread globally amid World War I. The U.S. government kept the outbreak secret, such that word of mouth, in essence, became the main tool for pandemic surveillance. It was labeled the Spanish flu, she said, because Spain, a neutral country an ocean away, was the first to describe it publicly.

The illness would ultimately infect about a third of the world’s population and kill an estimated 50 million.

In the 1957 Asian flu outbreak, President Dwight Eisenhower refused to mobilize government resources for a national campaign to administer the newly developed flu vaccine. He believed the private sector would respond better, Walensky said. The virus caused 115,000 U.S. deaths and between 1 million and 4 million worldwide.

“President Eisenhower was devoted to private solutions to such emergencies, and these were manifestly inadequate,” Walensky said. “About 30 million people got vaccinated. Keeping in mind the population of the U.S. at the time was 157 million, that was really only about 18 percent coverage.”

Today, she said, the political environment remains difficult despite the recent experience with COVID-19. The CDC, for example, is required to rapidly respond to outbreaks, but reporting from the states to the CDC is voluntary, and some states report more thoroughly and regularly than others.

Flu vaccination rates are another challenge, she said. Only 50 percent of Americans get flu vaccines, and the divide between the people who get vaccinated and those who don’t is largely determined by insurance coverage.

“There’s one really important thing about who gets vaccinated for influenza, and this has been a problem since Eisenhower, and that is if you’re insured,” Walensky said. “What we know is during the public health emergency we were able to put 370 million vaccine doses into 230 million American arms. The CDC has 14 recommended vaccines for adults, and the people who get them are the people who are insured.”

The federal government has a program to boost vaccination rates among children. Begun in 1994, the CDC purchases discounted vaccines and distributes them to state and local health departments in order to vaccinate more children — including those who are uninsured. The program has been stalled for two years by a lack of funding, Walensky said.

“The reason that’s important is the risk of another pandemic is real. We were handed a COVID-19 pandemic when everybody thought an influenza pandemic might be our next pandemic,” Walensky said, warning about avian flu, still largely confined to birds. “But just because we got COVID does not mean we are not getting influenza. We’ve had the largest avian flu outbreak ever, I believe, over the last year or two.”

The political climate is difficult enough, Walensky said, that some state health officials have warned the CDC against too vigorous vaccination campaigns, saying they could actually be counterproductive. In addition, some states today are making it easier for families to claim religious exemptions to childhood vaccine requirements, and fewer children are entering kindergarten fully vaccinated now than in years past.

“We’ve made century-long advances in understanding influenza, its pathogenesis, surveillance, and vaccine development, but little progress has been made in the social challenges that have and continue to limit the impact of our scientific progress,” Walensky said. “Failing to learn the lessons of prior pandemics has left us with a consistently fractured healthcare, public health, and vaccine-distribution system.”