What do you call the act of purposely spreading a disease to another person? For example, parents would try to get a child with chickenpox to transmit the disease to other healthy children. What do you call this practice? Is there a scientific term or a non-scientific term for it?
At one time people intentionally sought to be infected when they were in otherwise good health, in hopes of getting a mild case and then having immunity. This was a sort of proto-vaccination. It has not been current practice for over 100 years.
To give someone a disease, whether with good or bad intent, is to "infect" that person. One might say "intentionally infect" to distinguish from the accidental kind. One might also say "carelessly infect" or "negligently infect" when proper precautions were not taken.