What is the term for a carrier that has never had the disease but can pass it on?

The term for a carrier that has never had the disease but can pass it on is known as a passive carrier. This type of carrier can harbor and transmit pathogens without having an active infection themselves. Passive carriers may come into contact with the disease organism and inadvertently spread it to others, often without any symptoms or awareness of being a carrier.

In contrast, other types of carriers include active carriers who are currently infected and may show symptoms, and convalescent carriers, who have recovered from an active infection but still harbor the organism. The concept of an incubating carrier refers to an individual who is in the incubation period after infection but before the onset of symptoms. Thus, passive carriers are distinctive in that they do not experience the disease and yet can still facilitate its spread.