I rarely cover the history of medicine here, but it is fascinating to read the account here. They dressed the plague doctors up like this:
Which is to say the costume wasn’t entirely useless. “The ankle-length gown and herb-filled beak… would also have offered some protection against germs,” especially since its herbs were sometimes lit on fire and allowed to smolder, sending billowing smoke from the plague doctor’s face. (The satirical engraving above from 1700 mocks this practice.)
“The appearance of one of these human-sized birds on a doorstep could only mean that death was near.”This particular design has been credited to a French doctor, Charles de Lorme, said to have invented it in 1619.
“De Lorme thought the beak shape of the mask would give the air sufficient time to be suffused by the protective herbs before it hit the plague doctors’ nostrils and lungs.” Often mistaken for Medieval or Renaissance garb, the plague doctor costume is, in fact, a modern piece of kit.The Strange Costumes of the Plague Doctors Who Treated 17th Century Victims of the Bubonic Plague | Open Culture
Here’s another one for a good measure: