The provision of clean water, proper drainage and sewage systems and the appointment of a Medical Officer of Health in every area. Over time all of these have changed
The best way to get accurate information on the risks of a new health-enhancing activity is to consult someone who is informed and experienced in that activity and it is a good idea to consult your doctor about the activity before participating in it to make sure you are physically capable of doing so.
The answer will be immunity.