A new mouse virus causing necrosis of the thymus in newborn mice.

A new mouse virus has been recovered from laboratory and wild mice. The agent induces a non-fatal disease in infant mice, characterized by acute massive necrosis of the thymic medulla and cortex, granulomatous reaction, and subsequent restoration of essentially normal architecture with scarring. Intranuclear inclusion bodies are produced. Virus may persist in tissues of convalescent mice for many months. Electron micrographs of acutely infected thymuses showed nuclear and cytoplasmic karyoannular particles and masses of parallel fibrils in nuclei.