NIOSH Investigates Workplace Outbreak of Blastomycosis

The National Institute for Occupational Safety and Health (NIOSH) at the Centers for Disease Control and Prevention (CDC) is investigating a blastomycosis outbreak among workers at the Billerud Escanaba Mill, a paper mill in Escanaba, Michigan. Management from the paper mill requested a health hazard evaluation to investigate the outbreak and help to control it.

The goal of a health hazard evaluation is to learn whether workers are exposed to health or safety hazards on the job and to make recommendations to workplaces to prevent work-related injury and illness by controlling hazards. Health hazard evaluations can address many types of hazards including chemical, biological, physical, radiological, and others. Employees, employee representatives (unions), or employers can ask NIOSH to determine if health hazards are present in their workplace.

Blastomycosis is an infection caused by a fungus called Blastomyces. The fungus lives in the environment, particularly in moist soil and in decomposing matter such as wood and leaves. In the United States, the fungus mainly lives in the midwestern, south-central, and southeastern states, particularly in areas surrounding the Ohio and Mississippi River valleys, the Great Lakes, and the Saint Lawrence River. People can get blastomycosis after breathing in the microscopic fungal spores from the air, often after participating in activities that disturb topsoil or decaying plant materials like wood or leaves. Blastomycosis does not spread through the air between people or between people and animals.

NIOSH is conducting the health hazard evaluation to investigate the outbreak at the paper mill. NIOSH is coordinating its investigation with management from Billerud Escanaba Mill, unions representing employees, officials from the Michigan Department of Health and Human Services and Public Health Delta & Menominee Counties, and the Mycotic (fungal) Diseases Branch of the Centers for Disease Control and Prevention (CDC).

A NIOSH field team traveled to the facility for an onsite evaluation on March 27–28, 2023. The NIOSH field team, consisting of a health scientist, industrial hygienist, epidemiologist, laboratorian, and medical officer, was accompanied by CDC fungal disease experts and local and state health officials. During the evaluation, the field team:

• Held an opening meeting with Billerud Escanaba Mill management and union and employee representatives to discuss evaluation objectives.
• Performed a walkthrough of the worksite that occupies roughly 2,200 acres. The walkthrough included a detailed guided tour of the facility to understand work processes, practices, and personal protective equipment used by employees.
• Spoke with the company occupational health physician and nurse as well as employees and management to understand the work process, potential sources of exposure, and health concerns.

Based on findings during the initial onsite evaluation, NIOSH provided an interim letter to the employer, recommending the following actions to reduce the potential for exposure to Blastomyces while the health hazard evaluation is ongoing:

• Continue to make NIOSH approved N95® disposable filtering-facepiece respirators available to all employees for voluntary use to minimize exposure to Blastomyces, especially for employees who have underlying medical conditions or are on medications that might impair their ability to resist infection and put them at greater risk for severe illness.
• Inspect heating, ventilation, and air conditioning systems, and follow the manufacturers’ recommended maintenance schedules.
• Contract with a licensed ventilation engineer or building scientist to inspect ductwork for water incursion or microbial growth.
• Limit activities that involve disrupting soil, such as excavation.
• Continue to encourage employees who develop symptoms to seek care from their healthcare provider.

NIOSH investigators traveled to Escanaba, Michigan again in late April. During this trip, investigators offered employees a Blastomyces urine antigen test and the opportunity to participate in a work and health questionnaire. The urine antigen test is a screening test to look for potential exposure to Blastomyces and may help to identify additional cases. However, a positive test alone is not enough to diagnose the illness blastomycosis. Employees with positive urinary antigen tests or possible symptoms will be advised to see their personal healthcare providers for appropriate follow up care. The questionnaire will help to better understand what factors increase workers’ risk for infection. Employee participation was voluntary.

Investigators also collected environmental samples including soil samples, dust samples, wood chips, and ventilation system filter material so they can be tested for presence of Blastomyces. Unfortunately, there aren’t well-established ways for doing this, so interpretation of the results might be difficult. Even though this testing may not be fully informative about the cause of the outbreak, we think it was important to try because it might help in guiding prevention and control efforts.

NIOSH investigators will continue to work closely with CDC’s Mycotic Diseases Branch and state and local health departments during this evaluation. Next steps are:

• Contact people who were diagnosed with blastomycosis that investigators were unable to see during the medical survey in Escanaba to give them the opportunity to complete the confidential work and health questionnaire.
• Provide all employees who participated in having the urine antigen test with their individual test results as soon as possible after they are received from the laboratory.
• Begin data analysis and provide summary reports to the company as information becomes available.
• Continue to support Billerud management by providing information and recommendations to protect employee health and safety during the mill’s return to operation.

The evaluation will be completed as soon as possible. Following the evaluation, NIOSH will share a final report, which includes any findings and recommendations. The report will be made available to the public on the NIOSH website and shared widely with partners, including the:

• Employer
• Employees
• Unions representing employees
• Occupational Safety and Health Administration (OSHA)
• Michigan OSHA-approved state plan (MIOSHA)
• Public Health Delta & Menominee Counties
• Michigan Department of Health and Human Services

Public Health, Delta & Menominee Counties Information