Final answer:
The manager must exclude the employee from handling food if they have been diagnosed with hepatitis A, even if they are asymptomatic, to prevent the spread of the virus and protect public health.
Step-by-step explanation:
If a food service employee has been diagnosed with the hepatitis A virus but is not showing signs of illness, the manager must exclude the employee from handling food. This is because hepatitis A can be transmitted through the fecal-oral route and by consuming contaminated food or water. As a preventive measure to protect public health, it is critical to ensure that any person diagnosed with hepatitis A is not involved in the preparation or serving of food until they are cleared by a health professional.