An outbreak of mouse hepatitis virus (MHV) has been identified in animals from the Animal Production Area (APA) at NCI-Frederick. On Jan. 30, the University of Missouri diagnostic lab informed APA staff that some mice sent from Building 1029 on Jan. 23 for routine testing were showing borderline antibody levels to MHV. On Feb. 2, additional animals were sent from Building 1029 to the Animal Health Diagnostic Laboratory (AHDL) where antibodies to MHV were detected in the sera. All previous routine testing for MHV had been negative.

Building 1029 was immediately quarantined and all shipments stopped. The building has since been depopulated and is being decontaminated. The building housed DBA/2NCr, BALB/cAnNCr, C3H/HeNCr MTV-, Sencar A/PtCr, and CD2F1Cr mice. Mice from Building 1029 had been distributed to numerous animal facilities on both the Frederick and NIH campuses as well as to other organizations throughout the United States.

All 25 known strains of MHV are highly contagious within mouse colonies and easily transmitted in feces and by direct contact, aerosol, and fomites. An MHV infection typically runs its course in immunocompetent mice within three weeks. However, immunocompromised mice tend to develop chronic infections, sometimes leading to death.

By the end of the day on Feb. 4, all organizations that had received mice from Building 1029 since Dec. 15, 2003, had been notified of the MHV outbreak. All NCI investigators who received mice from Building 1029 were notified by the animal facility managers that they might have received MHV-positive animals. NIH facility veterinarians who had received animals from Building 1029 were also notified of the outbreak. On Feb. 6, all recipients of APA animals, even those who did not receive animals from Building 1029, were notified of the outbreak.

All rooms in NCI facilities that received mice from Building 1029 have been quarantined, and all shipments to and from these NCI animal facilities have been stopped. Mice that were received from Building 1029 from Dec. 1, 2003, to Feb. 2, 2004, were removed to AHDL and tested for the presence of antibody to MHV. Serologic tests from these mice confirmed the presence of antibody to MHV in some mice that had been shipped from Building 1029 to the NCI animal facilities. Additional mice testing is being conducted to determine the extent of the outbreak and/or whether containment efforts have been successful.

Investigators should be aware that all tissues taken from mice obtained from or in contact with mice from Building 1029 should be tested for the presence of MHV prior to distribution or reintroduction into any NIH animal facility.

If you have any questions regarding the MHV investigation please call Dr. Rick Bedigian, director, Laboratory Animal Sciences Program, at (301) 846-1542.