GRAND RAPIDS, Mich. (WOOD) — The owners of an Escanaba paper mill at the heart of a rare fungal outbreak have elected to temporarily shut down the mill for three weeks.

Billerud is a Swedish pulp and paper manufacturer that owns nine facilities across three countries, including three in the United States. Company officials announced Thursday night that the shutdown is a precaution to try and prevent any additional blastomycosis exposures.

“Our top priority now and always is protecting the health and safety of our employees and contractors who work at our Escanaba Mill,” Billerud President Christoph Michalski said in a statement. “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 the National Institute for Occupational Safety & Health and other organizations, which requires larger portions of the mill to be vacant while this work is performed.”

According to Billerud, the company was first notified about possible blastomycosis infections on March 3. The local health department for Delta and Menominee Counties was notified by a local hospital that they had found several atypical pneumonia infections, all from people affiliated with the mill.

Follow-up testing, which can take a couple of weeks, confirmed that some of the infections were caused by blastomycosis, a type of fungus that grows in moist soil and decomposing matter. People are infected by directly breathing in the fungal spores, meaning it cannot spread from person to person.

The health department first announced they were investigating an outbreak involving 15 people on March 9. By April 4, the number was up to 81 likely infections, with 19 confirmed and 62 suspected cases. Billerud says there are now 21 confirmed cases and 76 probable infections.

A blastomycosis infection often comes with many symptoms, including fever, chest pain, fatigue, muscle and joint pain, night sweats, difficulty breathing and a severe cough that may occasionally produce blood.

Not everyone who breathes in the spores will develop an infection, but those that do are typically treated with an antifungal medication.

Michigan’s Upper Peninsula is a known risk area for blastomycosis infection. However, an official with Public Health Delta & Menominee Counties says there has never been an industrial outbreak like this documented in the U.S.

The fungal spores are launched into the air when they are disturbed. So, PHDM recommends wearing an N95 mask when working in or around moist or disturbed soil or in heavily wooded areas. It also recommends waiting to move leaf litter until it is dry and avoiding digging and disturbing soil on windy days.