The new leader of the nation’s coronavirus fight has been battling diseases her whole career

Dr. Rochelle Walensky tackled the AIDS epidemic, rose through the ranks at Massachusetts General Hospital, and now heads the CDC.

Dr. Rochelle Walensky.Kate Flock/MGH

The unit where Dr. Rochelle Walensky performed her residency, during the peak of the AIDS epidemic in Baltimore, held a standing memorial service every two weeks because so many of its patients were dying.

It was a grueling start to a medical career, when young trainees worked 100-hour weeks at Johns Hopkins Hospital, holding the hands of people succumbing to a virus for which there was not yet any treatment.

“In 1995 we told patients with AIDS they would, with certainty, die,” Walensky said in 2019 testimony before Congress. Since those early days, the physician has had a meteoric rise at Massachusetts General Hospital, including being appointed just the third chief — and the first woman — to lead the Division of Infectious Diseases since its inception in 1956.

Now, as the newly appointed director of the Centers for Disease Control and Prevention in the Biden administration, the longtime Boston doctor is again fighting a virus that is out of control. In Baltimore she was just a resident; this time she is leading the nation’s response.

It’s her early training, and her many years in the field of HIV, that have prepared her for a fight that is all too familiar, more than a dozen close friends and colleagues in academia and the medical world told the Globe.

“Those formative years were really hard, and to see what she has been able to turn them into has been so inspiring,” said Kelly Gebo, a physician at Johns Hopkins and close friend since medical school.

In her first few weeks on the job, Walensky, 51, has already found herself at the center of the fraught politics surrounding this pandemic. She is taking over an agency with a tarnished reputation, where science had taken a back seat to Trump administration politics, as she noted in a New York Times op-ed last month. She is being called upon to fight new variants of the virus even as she cleans up the mess she inherited, saying earlier this month that the agency did not even know exactly how much vaccine supply it had.

The CDC declined to make Walensky available for an interview.

Several friends and colleagues said they have kept in touch with Walensky through brief messages and congratulatory e-mails as she has started her new role. She appreciates the gravity of the challenge before her, said Kenneth Freedberg, her longtime MGH collaborator.

“She feels some responsibility to right a ship that really was listing badly and I think she’s doing it quickly and it will be moving straight very quickly,” he said.

Walensky must not only manage an out-of-control pandemic that is ravaging a country that is more politically divided than ever, but she must also restore the confidence of career scientists within the CDC who felt sidelined during the Trump administration.

She has already found herself in the crosshairs of that national tension, specifically over how to reopen schools. She met strong backlash from teachers unions earlier this month after saying it was not necessary for teachers to be vaccinated in order to reopen schools. The White House initially distanced itself from Walensky’s remarks, then reversed course and appeared to back her position.

Late last week, the CDC released much-anticipated school reopening guidelines to mixed reactions. Teachers unions largely applauded the guidance, which recommended full in-person learning only when community transmission of the virus is low, but other reopening advocates said they were too strict and will keep many schools closed or hybrid.

“She does not cower, she does not back down,” said Raphael Landovitz, a physician at the University of California Los Angeles who has known Walensky since her Baltimore days.

Over the past year she has been a leader in Massachusetts’ war against the pandemic, at MGH and more broadly, serving on Governor Charlie Baker’s COVID-19 Advisory Board.

This summer Walensky was instrumental in conducting the research that provided colleges and universities in the area with a roadmap for how to safely reopen their campuses through the use of frequent asymptomatic testing. That led to the first wide-scale use of surveillance testing in the Boston area and provided the basis for other organizations and businesses, and now public secondary schools, to adopt the same approach.

Rochelle Walensky spoke during a news conference in Delaware in December. Chip Somodevilla/Photographer: Chip Somodevilla/G

Working off Walensky’s research, colleges and universities came to understand that they could not control the behavior of students, but they could monitor it, and perhaps influence it, by using data. That concept, said infectious disease experts, is why there is perhaps no one better equipped than an HIV expert to lead the fight against this new pandemic, whose spread has been linked to social behavior.

Colleagues say her style was on display last week when she warned the public about traveling.

Instead of harsh edicts, Walensky first presented the staggering numbers of deaths and new cases, then crafted her warning using what was, to her colleagues in the fight against HIV, unmistakably a harm-reduction approach.

“Now is not the time to travel,” she said calmly. “But if you must travel, you must wear a mask... to protect yourself and others while you travel.”

“I watched that press conference and I thought, ‘yeah, this is an HIV doctor talking,’ ” said Monica Gandhi, a professor and infectious disease physician at the University of California San Francisco, who served with Walensky on a federal AIDS research advisory council several years ago. “HIV doctors have learned over 30 years how to message with nuance, with compassion, and acknowledge the real-world aspects of people’s lives.”

On the front lines of this new pandemic, Walensky has also battled stark disparities in access and care that are similar to what she first witnessed 25 years ago in Baltimore. While patients from across the country sought out Johns Hopkins for its renowned services, Walensky’s unit cared for residents of downtown Baltimore who were already suffering from the ravages of substance use disorders, blight, and poverty. MGH saw a similar surge at the onset of the coronavirus pandemic, especially from Chelsea, home to many Spanish-speaking immigrants and a city that has been disproportionately ravaged by the virus. In April, about four in 10 of the hospital’s coronavirus patients were Spanish-speaking.

“These issues around equity and around disparities are very much central to her understanding of illness and health and health care,” said Freedberg, her longtime MGH partner.

Walensky has been internationally respected in her field for decades. Much of her work involves calculating the costs of HIV treatments, always coming back to the question of how to do the most good for the most people, colleagues and collaborators said.

“She’s just such a clear thinker, really listens to other people’s opinions and is able to synthesize data on the spot and help direct the research,” said Judith Currier, an infectious disease physician at the University of California Los Angeles who directs the AIDS Clinical Trials Group. Currier said the work of Walensky and Freedberg has been instrumental in determining the cost effectiveness of different treatment strategies for HIV.

During the second year of her residency in Baltimore, thanks to newly available drugs, HIV morphed from an incurable terminal condition to a treatable chronic condition with a normal life expectancy. The change was startling to behold, said Gebo, who performed her residency alongside Walensky.

Suddenly there was hope on that unit that had felt like the last stop before death.

Stuart Ray, a physician at Hopkins Hospital who was chief resident during Walensky’s residency, has watched generations of trainees pass through that ward, but Walensky stands out as unique in his memory.

“Rochelle stands out as someone who right away wanted to know what she could do better, who wanted to chase problems to the ground,” he said.

As a clinician, professor, researcher, MGH administrator, and the mother of three boys, Walensky has achieved her success in part by mastering the art of balancing. Now she is doing that as she commutes between Boston, Washington, and CDC headquarters in Atlanta.

“She is amazing at juggling.” Gebo said. “We have an expression — we have to remember which balls are glass. No one wants those to drop.”