Mouse hepatitis virus and minute virus of mice are never subclinical.

• A. True
• B. False
• C. They can be subclinical depending on conditions
• D. Not enough information

Answer: (B)

Subclinical infections are possible with these viruses, and disease expression depends on the animal’s age, immune status, and the viral strain. Mouse hepatitis virus (a coronavirus) can cause severe hepatitis and neurologic disease in suckling or stressed/newly infected mice, but in adult, immunocompetent mice it often produces no obvious signs or only mild illness. Minute virus of mice (a parvovirus) typically causes little disease in healthy adult mice, though it can cause problems in fetuses, newborns, or immunocompromised animals. Because both viruses can be present without clinical symptoms under common lab conditions, the statement that they are never subclinical is not correct.