When your boss goes to work sick (as the CEO at my last two companies did), it signals its ok to the rest of the employees. Ignorance plays a large role as well

When your boss goes to work sick (as the CEO at my last two companies did), it signals its ok to the rest of the employees. Ignorance plays a large role as well. Commonly (IME), someone with a viral cold gets antibiotics and goes to work the next day thinking they are no longer contagious.