Blastomyces Urine Antigen Testing for Active Case Identification During a Blastomycosis Outbreak.

Area of Science:

• Mycology
• Infectious Diseases
• Public Health Surveillance

Background:

• Blastomycosis is a fungal infection endemic to North America.
• Accurate and timely diagnosis is crucial for effective outbreak management.
• The utility of urine antigen testing for active case identification during outbreaks remained unclear.

Purpose of the Study:

• To evaluate the effectiveness of blastomycosis urine antigen testing for identifying cases during a 2023 outbreak.
• To assess demographic and clinical factors associated with positive urine antigen test results.
• To determine the suitability of urine antigen testing for detecting mild and asymptomatic infections.

Main Methods:

• A cross-sectional study was conducted among 603 employees at a Michigan paper mill following a recognized blastomycosis outbreak.
• Urine antigen testing was performed on 95% (n=578) of employees.
• Data on work history, health status, and blastomycosis-like symptoms were collected and analyzed for association with test positivity.

Main Results:

• Of 578 tested employees, 9% (n=52) tested positive for blastomycosis urine antigen.
• The testing identified 25 previously undetected cases.
• Blastomycosis-like symptoms (p<0.001) and recent hospitalization (p=0.02) were associated with test positivity; 10% of positive cases were asymptomatic.

Conclusions:

• Blastomycosis urine antigen testing is a sensitive and acceptable method for identifying cases during an outbreak.
• The test effectively identified additional cases, including asymptomatic infections, contributing to public health surveillance.
• Further research is recommended to fully understand its role in detecting milder or subclinical infections during outbreak investigations.