A Michigan mill worker has died and at least a dozen other people have been hospitalized due to an outbreak of a rare fungal infection, according to local health officials.

Public health officials say 21 confirmed and 76 probable cases of blastomycosis have been identified in connection with the Billerud Paper Mill in Escanaba, Michigan. The fungus, which can thrive in decaying wood, is not infectious person-to-person, but people who inhale spores can get infected.

Symptoms from an infection include fever, fatigue and cough and severe cases can impact the lungs or spread to other parts of the body.

The mill employs about 800 people and all 97 confirmed and probable cases in the outbreak are in known employees, contractors or visitors to the plant.

“Everyone at Billerud is deeply saddened by this news,” said Brian Peterson, Billerud operations vice president for the mill, in a statement. 

“Anyone who works at our facility is part of our team, and we are keeping this individual, their family, coworkers and friends in our thoughts and close to our hearts,” he added.

Blastomycosis is a relatively rare fungal infection. About 240 cases were reported nationwide in 2019.

A Centers for Disease Control and Prevention (CDC) study found that the fungal infections were more common in the Upper Midwest, with higher rates of infection in Minnesota and Wisconsin than other states.

It’s unknown exactly when the infections began at the paper mill, but CDC investigators first visited the plant last month and recommended additional safety measures like use of N-95 masks.

The mill will be temporarily closed as it is cleaned.

“As a precautionary measure, we will temporarily idle the Escanaba Mill for up to three weeks to facilitate additional proper cleaning based on recommendations from NIOSH and other organizations, which requires larger portions of the mill to be vacant while this work is performed,” Christoph Michalski, Billerud’s president and CEO, said in a statement Thursday.