Ben Harding/iStockBy MEREDITH DELISO, ABC News(NEW YORK) — The head of one of the largest regional health systems in the Midwest announced his retirement this week, following a controversy over recent statements he made about COVID-19.Sioux Falls, South Dakota-based Sanford Health announced Tuesday it has parted ways with longtime CEO Kelby Krabbenhoft.The announcement comes after Krabbenhoft sent an email on Nov. 18 to health system employees, saying he won’t be wearing a mask at work because he recovered from COVID-19. The letter was obtained by several news organizations, including the North Dakota-based wire service Forum News Service, which printed it in full.Sanford Health distanced itself from Krabbenhoft following the email’s publication.“Kelby Krabbenhoft’s email was based on his own experience with COVID-19 and his personal opinions about the virus. They do not reflect the views of our health system as a whole,” the organization said on Twitter on Nov. 20. We continue to be incredibly grateful to our frontline workers who are stepping up every day to take care of our patients. (3/3)— Sanford Health (@SanfordHealth) November 20, 2020In a news release Tuesday, Sanford Health officials did not mention the email, merely saying that the organization and Krabbenhoft have “mutually agreed to part ways.”“Kelby’s impact on the organization and the communities it serves will be felt for generations to come,” Board of Trustees Chair Brent Teiken said in a statement.In a statement sent to the Sioux Falls ABC affiliate KSFY-TV, Krabbenhoft said now was “a good time to retire.”“Sanford is in a good place, strongest ever,” said Krabbenhoft, who had served as president and CEO since 1996. “It is Thanksgiving week and almost exactly 25 years since my family came here. It is a good time to say ‘goodbye.’”Sanford Health’s network includes 46 hospitals, spanning 26 states and 10 countries. It requires clinic employees, patients and visitors to wear masks, according to its website.According to the copy of the email obtained by Forum News Service, Krabbenhoft said that people who have not yet contracted the virus should wear a mask.“It is important for them to know that masks are just plain smart to use and in their best interest,” the email said.But for him to wear a mask “sends an untruthful message that I am susceptible to infection or could transmit it,” he wrote, adding that he had “no interest in using masks as a symbolic gesture.”In the email, Krabbenhoft, who is not a physician, also said that he is immune to COVID-19 for at least seven months “and perhaps for years to come.”Much is still unknown about COVID-19 immunity, though based on other coronaviruses, “people appear to become susceptible to reinfection around 90 days after onset of infection,” according to the CDC.COVID-19 reinfection is “rare,” though such cases have been reported, the CDC noted. It recommends that people wear a mask in public “whether you have had COVID-19 or not.”Krabbenhoft told Sioux Falls station KELO-TV last week that his email was misinterpreted.“All I did in my letter was, again, in a hopeful way, in a positive way, as a recovering virus patient, suggest that there is a growing body of evidence and discussion about the longevity of the immunity that is garnered from this. That’s all I said,” he told the station, citing a New York Times piece on new COVID-19 immunity research that was published earlier this month.The turnover at Sanford Health comes as South Dakota is experiencing a surge in hospitalizations. The state has the highest rate of hospitalizations in the United States, according to the COVID Tracking Project, with 649 hospitalizations per 1 million people.South Dakota Gov. Kristi Noem has not issued any restrictions or a statewide mask mandate during the coronavirus pandemic. Last week, Sioux Falls officials approved an ordinance requiring masks inside retail businesses and city facilities when social distancing cannot be maintained.Copyright © 2020, ABC Audio. All rights reserved. Kelby Krabbenhoft’s email was based on his own experience with COVID-19 and his personal opinions about the virus. They do not reflect the views of our health system as a whole. (1/3)— Sanford Health (@SanfordHealth) November 20, 2020“Sanford Health’s position is the same as it has always been – consistently wearing masks, avoiding crowds and staying home if you’re sick are critical to preventing the spread of the virus. It is important to follow [Centers for Disease Control and Prevention] guidelines,” it continued.