An infected organism that does not show symptoms during the spread of an illness is known as a:

The term that accurately describes an infected organism that does not show symptoms during the spread of an illness is "carrier." A carrier is an individual who harbors a pathogen without manifesting the clinical symptoms of the disease. They can still spread the pathogen to others, potentially leading to further outbreaks. This concept is significant in public health, as carriers can contribute to the transmission of disease without being detected, making it crucial for health officials to identify and manage such individuals to control the spread of infectious diseases.

In contrast, a reservoir refers to the natural habitat in which a pathogen lives and multiplies, such as humans, animals, or the environment. A parasite typically denotes an organism that lives on or within a host and derives nutrients at the host's expense, often causing harm to the host. A host is a general term for any organism that supports the survival and growth of a parasite or pathogen. While both reservoirs and hosts are essential in disease dynamics, they do not specifically describe the asymptomatic spread characteristic of carriers.