Final answer:
Food workers diagnosed with Hepatitis A require a doctor's note to return to work because it can be transmitted through food and poses a significant health risk.
Step-by-step explanation:
A doctor's note will be necessary to return to work if a food worker has been diagnosed with Hepatitis A. This condition poses a high risk of contamination and spread in a food service environment, as it can be transmitted through the handling of food. Hepatitis A is a viral infection that causes inflammation of the liver and can be spread when an infected person handles food without proper hygiene. Unlike the common cold, seasonal allergies, or a minor headache, which are either low-risk illnesses or non-communicable, Hepatitis A can have significant health implications for others if proper precautions are not taken.