Objective: After an employee at a cancer research institute was diagnosed with lymphocytic choriomeningitis, an investigation was performed to determine the extent of lymphocytic choriomeningitis virus (LCMV) infections among the institute's employees and to identify risk factors for infection.
Design: Retrospective cohort study.
Setting: A US cancer research institute.
Participants: Eighty-two of 90 institute employees.
Main outcome measures: Serum LCMV antibodies.
Results: Seven workers (9%) with definite LCMV infection (LCMV IgG antibody titer greater than or equal to 16) and one worker (1%) with probable infection (IgG titer = 8) were identified (10% overall seroprevalence). All infected employees handled animals or animal tissues and were more likely than other animal handlers to have worked with nude mice (Mus musculus) (P less than .02). Among the 31 employees who worked with nude mice at the institute, infected workers were more likely to clean the cages of nude mice (P much less than .001), change their bedding (P less than .01), and change their water (P less than .001). The institute had been injecting nude mice with LCMV-infected tumor cell lines and had recently increased the nude mouse population and the duration of experiments. These changes would have increased the LCMV burden at the facility and were temporally associated with the cluster of LCMV infections in employees.
Conclusions: This LCMV outbreak, the first reported since 1974, is the first associated with nude mice. It illustrates the ongoing hazard LCMV poses in research laboratories. Since the symptoms of LCMV infection can be nonspecific, clinicians should consider this diagnosis in ill patients who report laboratory rodent exposure.