Quarantine field
From Memory Alpha, the free Star Trek reference.
The quarantine field is a medical invention that isolates a patient and/or the doctor and keeps them separate from the environment while providing them with a sterile surrounding.
Quarantine fields had not been perfected by the 22nd century. Doctors wearing surgical masks and gloves were a common sight back then. By the 24th century, medical procedures without the quarantine field were nearly unthinkable. (TNG: "A Matter of Time")
