MACKINAC ISLAND, Mich. (AP) — At least 15 people who attended a public affairs conference last week on Michigan’s Mackinac Island have tested positive for COVID-19, including U.S. Transportation Secretary Pete Buttigieg.

Pete Buttigieg, U.S. secretary of transportation, speaks during a news conference in the James S. Brady Press Briefing Room at the White House in Washington, D.C., US, on Monday, May 16, 2022. Senior officials and cabinet members from President Biden’s Infrastructure Implementation Task Force spoke on the six month anniversary of the Bipartisan Infrastructure Law. Photographer: Al Drago/Bloomberg via Getty Images

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The gathering is put on each year by a business group, the Detroit Regional Chamber, and attracts more than 1,000 public officials, journalists and others who discuss a variety of political and policy issues. Four Republican candidates for governor held a debate.

Participants were required to show proof of a COVID-19 vaccination or a negative test.

The Chamber said at least 15 people tested positive immediately following the event, The Detroit News reported. Buttigieg disclosed his infection Monday on Twitter, saying he had mild symptoms.

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Mackinac Island’s wastewater tested “fairly high” for evidence of COVID-19 just before Memorial Day, said Kerry Ott, spokeswoman for the local health department.

Gov. Gretchen Whitmer tested negative Monday, spokesman Bobby Leddy said.

David Eggert, a reporter at Crain’s Detroit Business, said on Twitter that “very few people” wore masks. He, too, was infected.

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