What term describes a pathogen that relies on a host for survival in a way that benefits the organism and harms the host?

The correct term for a pathogen that benefits from its host while causing harm to that host is "parasite." Parasites have a unique relationship with their hosts; they derive nutrients and other benefits from them, often leading to negative health effects for the host organism. This relationship can manifest in various forms, such as infections or diseases that can significantly affect the host's wellbeing.

For example, common parasites include organisms like tapeworms, which live in the intestines of their hosts and absorb nutrients from the host's diet, thereby harming the host's health over time. This contrasts with other types of pathogens, such as bacteria and viruses, which may cause diseases through different means but are not classified as parasites due to their different interactions with hosts. Fungi can also interact with hosts in harmful ways, but they typically do not fit the specific definition of a parasite that implies a symbiotic relationship where one organism thrives at the expense of another.