The nuns, ages 69 to 99, lived together across three floors at the Felician Sisters' convent in Livonia. They included teachers, an author and a secretary in the Vatican Secretariat of State, according to the Global Sisters Report, an outlet of the National Catholic Reporter publishing company.
"I first heard two aides had contracted the virus," Sister Mary Andrew Budinski, the superior of the convent, told Global Sisters Report. "We don't know who they are, and we don't want to know. Then it hit sisters on the second floor, and it went through like wildfire."
Twelve of the nuns died in one month between Good Friday, April 10, and May 10. The 13th nun died June 27; 17 others recovered.
The group said on Monday the coronavirus deaths, which wiped out 22 percent of the residents, "may be the worst loss of life to a community of women religious since the 1918 influenza pandemic."
The oldest, Sister Mary Luiza Wawrzyniak, 99, was the first. She died April 10.
Four others followed that week: sisters Celine Marie Lesinski, 92, and Mary Estelle Printz, 95, died on April 12; Sister Thomas Marie Wadowski, 73, on April 15; and Sister Mary Patricia Pyszynski, 93, on April 17.
The deaths continued in mid-April when Sister Mary Clarence Borkoski, 83, died April 20; Sister Rose Mary Wolak, 86, died on April 21; and Sister Mary Janice Zolkowski, 86, passed on April 22.
Sister Mary Alice Ann Gradowski, 73, died April 25; Sister Victoria Marie Indyk, 69, died April 26; and Sister Mary Martinez Rozek, 87, died on April 28.
Sister Mary Madeleine Dolan, 82, died May 10, Sister Mary Danatha Suchyta, 98, died June 27.
"They weren't giving us numbers," Andrew recalled. "Just every day, they'd say, 'Another sister.' 'Another sister.' 'Another sister.' It was very frightening."
Andrew herself contracted the virus and thought she would die at one point.
"I surrendered to that. I said, 'God, if you're going to take me, I'm ready.' Then I woke up the next morning and I was still alive. Then somehow, I got better," she said.
Global Sisters reported at least 19 other nuns have died of COVID-related complications in the U.S.
Michigan has recorded a total of 75,248 confirmed cases and at least 6,141 deaths due to the virus.