Heres a little history lesson, taken from the only and only reliable source….Wikipedia
A plague doctor was a physician who treated victims of the bubonic plague during epidemics. These physicians were hired by cities to treat infected patients regardless of income, especially the poor that could not afford to pay. Plague doctors are often depicted in Halloween costumes and seen as a symbol of death and disease.
Plague doctors had a mixed reputation, with some citizens seeing their presence as a warning to leave the area. Some plague doctors were said to charge patients and their families additional fees for special treatments or false cures. In many cases these “doctors” were not experienced physicians or surgeons; instead, being volunteers, second-rate doctors, or young doctors just starting a career. In one case, a plague doctor was a fruit salesman before his employment as a physician. Plague doctors rarely cured patients; instead serving to record death tolls and the number of infected people for demographic purposes.