What term describes an infection caused by two or more diseases?

The term that accurately describes an infection caused by two or more diseases is "mixed infection." This term is specifically used when a single site or region of the body is affected by multiple pathogens simultaneously. In a mixed infection, the pathogens can interact, potentially leading to more severe health outcomes than a single infection might cause.

Co-infection can also imply the presence of two infections occurring in the same individual, typically referring to two different pathogens infecting the body at the same time, but it doesn't emphasize the involvement of multiple diseases in the same anatomical location that a mixed infection does.

Superinfection refers to a situation where a second, often resistant, infection occurs on top of an existing infection. This occurs after the initial infection has been treated or modified, not simultaneously from the onset.

Secondary infection describes an infection that arises as a complication following an initial primary infection, not necessarily indicating that multiple pathogens are at work at the same time.

Thus, mixed infection is the preferred term as it distinctly conveys the simultaneous nature of multiple pathogens affecting an individual.