April 14, 2005 (CIDRAP News) – Despite 4 months of investigation, the source of bacteria that caused tularemia in three laboratory workers at Boston University remains a mystery, the Boston Public Health Commission (BPHC) has reported.The investigation into the three cases has led to some new safety precautions for microbiology researchers in the Boston area, however, according to the report by M. Anita Barry, MD, MPH, director of communicable disease control for the BPHC.In the coming months, the BPHC will take a number of steps to bolster monitoring and reporting of infectious diseases acquired on the job, noted John Auerbach, BPHC executive director, in the forward to the report. Steps include mandatory training, close monitoring of Boston University’s improvement efforts, and training for research laboratory personnel. Most of the changes affect microbiology lab researchers throughout the Boston area, not just at Boston University.The following account of the event and conclusions of investigators are taken from the 15-page report:While studying a relatively benign strain of Francisella tularensis last year, three lab workers at the university fell ill. Two got sick in May, the third in September. Their symptoms were consistent with tularemia, which can cause fever, chills, malaise, low back pain, and chest pain. F tularensis is also considered one of a handful of pathogens with potential to be used as a biological weapon.The illnesses weren’t reported until Nov 10. Authorities immediately launched an investigation that included the BPHC, the state health department, the Centers for Disease Control and Prevention (CDC), and the FBI.The investigation yielded some information on how the workers came to be infected through working with an attenuated laboratory strain not previously linked with human infection: they may have also been exposed to a wild strain of F tularensis found in some samples of their laboratory strain obtained from the University of Nebraska.But how the virulent bacteria found its way into the attenuated samples remains a mystery. The report said, “Testing at CDC continues in the effort to determine the time and place of contamination of the original vial. CDC is currently focusing its investigation on potential sources of the Type A tularemia outside Boston.”There is no evidence to suggest an intentional infection or contamination, Barry reported. However, she repeatedly noted concerns over a “routine failure to comply with safety protocols.”The report’s conclusions also include the following:The outbreak was limited to three people and never posed a risk to the publicFailure to spot and quickly report work-related illness in lab staff is a major concern for health officialsLaboratory infection control practices must be clearly documented and enforcedIn addition, the health commission is requiring that Boston University take several steps before it resumes tularemia research, including retraining workers on safety and modifying and strengthening standard operating procedures.