Kris Ehresmann, a key architect of Minnesota's response to the COVID-19 pandemic, will retire in February after more than 30 years at the state health agency.

Ehresmann, the state's infectious disease director, started at the Minnesota Department of Health (MDH) in the 1980s as a student worker. Since then she has held several key roles in the agency's infectious disease department and rose through the ranks to oversee more than 100 employees who monitor diseases spread by people and animals as well as from contact with contaminated food and water.

"Serving as the director of the infectious disease division has been one of the great honors of my life," Ehresmann said Thursday in the MDH announcement of her retirement. "Like so many people who have worked in a job they love, I have mixed feelings about saying goodbye. That said, it has been my privilege to work with an amazing team and I have every confidence I am handing the baton to the best in the business."

While most of the agency's work typically has been out of the public eye, the historic COVID-19 pandemic has thrust the epidemiologist into the spotlight. Ehresmann regularly spoke to the media and the public through briefings broadcast on the internet, usually accompanied by Minnesota Health Commissioner Jan Malcolm.

"Kris Ehresmann has played a huge role in public health not only in Minnesota but nationally," Malcolm said. "I have the highest regard for her skill as a public health worker, a communicator and a leader. She has helped guide Minnesota through many difficult public health challenges, and along the way she cultivated a new generation of talented public health leaders within MDH and across the state."

Ehresmann's retirement announcement did not specify her reasons for leaving or her future plans. In an interview with the Star Tribune in late December, she said 2021 had been a year of many emotions, including sadness that the hope brought on by the introduction of vaccines faded as first delta, then omicron, took hold and vaccine hesitancy became stronger.

"We started the year with optimism because we thought we had the tools," she said. "That was just the most amazing thing. But we became so discouraged with every day when we saw death after death that is preventable."

Her departure comes as Minnesota residents, governments and businesses grapple with the fast-spreading COVID-19 omicron variant. Another 11,440 new infections and 78 more fatalities were announced by MDH on Thursday, including the death of a Dakota County adolescent.

Some COVID-19 models, including one from Mayo Clinic, predict that case growth could peak in the next few weeks. If the predictions hold true, Minnesota could still see significant rates of new infections even as the variant recedes. The state's test positivity rate stands at a record high of 23.7% compared with the most recent low of about 1% last June before the delta variant took hold.

Wastewater samples indicate the amount of COVID-19 genetic material has fallen more than 60% over the last two weeks, according to data released Thursday by the Metropolitan Council, which analyzes water processed at the metro plant. Case rates tend to lag wastewater trends by six to eight days.

Public health leaders said that even with Ehresmann's retirement, MDH has a deep bench of expertise and experience to continue its work in disease monitoring, prevention and education.

"The public has benefited from the stability, confidence and wisdom that Kris has brought to her role," said Craig Hedberg, a public health professor at the University of Minnesota. "These qualities can flourish when leaders like Kris have the opportunity to grow in their roles. We will miss her greatly but are confident that she represents a legacy that will continue to produce excellent leadership for many years to come."

Ehresmann received her bachelor's degree in nursing from St. Olaf College, and a master's of public health in epidemiology from the University of Minnesota.

In addition to her work at MDH, she has served on several national public health committees, including the Advisory Committee on Immunization Practices, which advises the Centers for the Disease Control and Prevention. At the time of her appointment in 2008, she was only the second nurse ever named to that advisory panel.

"She's been a great asset for Minnesota even before the pandemic and certainly has done a lot of things for the state both nationally and behind the scenes," said Dr. Randy Rice, president of the Minnesota Medical Association.

Gov. Tim Walz said Ehresmann's retirement will be a "big loss."

"The team over there is solid, they are good," he said. "It's always hard to lose a longtime civil servant, but I have to tell you after the last two years ... Kris Ehresmann has certainly earned a well-deserved retirement. And we'll miss her."

Emily Emerson, the assistant director of the Infectious Disease Epidemiology, Prevention and Control Division, will become interim director while MDH conducts a national search for Ehresmann's replacement.

Ehresmann and her team regularly monitor emerging infectious diseases. When the first reports of what would be named COVID-19 came out of China in December 2019, she did not know what to expect.

"There have been other novel viruses that have come and haven't had the same impacts," Ehresmann told the Star Tribune in June 2020. "By February [2020] I knew that this was going to be really different.

"I don't think I fully comprehended how different it would be."

Staff writer Jessie Van Berkel contributed to this report.