Semiannually, and more often, if in its judgment necessary, the board of health of a city or general health district shall inspect the sanitary condition of all schools and school buildings within its jurisdiction, and may disinfect any school building. When a dangerous communicable disease is unusually prevalent and verified positive cases of the disease have been documented in a specific school building, the board may close that specific school building for such time as is necessary to disinfect the building or otherwise bring that specific school building into sanitary condition.