Biosecurity measures are paramount on any production farm or feedlot, especially when working with dairy calves as you need them to thrive and produce a profit in the long run. While calves may be carrying diseases and showing no symptoms at the beginning, they are still able to pass on the disease to humans for certain zoonotic diseases. If a farm worker were to be infected with a zoonotic disease and went on to spread the disease to all of the other cattle he worked with on any given day, it would be detrimental to that farm's supply.
Perhaps the most important control point to lessen spread of disease between dairy calves and humans is to either have the workers wear and change gloves between the handling of each calf, washing hands after working with one calf, or being as hands off as possible while also keeping the calf hutches and their equipment clean (IA State).
Elderly and immunosuppressed workers are more likely to contract a zoonotic disease and may be able to spread the disease easier than normal, therefore it would be worth it to understand who is handling the animals on a farm or feedlot (IA State).
In the long run, prevention is more effective and appropriate than trying to cure a human and animal of a zoonotic disease (Oregon VMA). It is advised to be up to date on vaccinations, as well as taking proper biosecurity measures: wash boots if permitted, wear gloves, wash hands regularly, work with quarantined calves solely or as your last task as to not infect your healthy cows, and be cognizant of your clothes and boots and how dirty they are before you complete other tasks (Milk Production).