A pathogen that is able to establish an infection in an otherwise healthy host is referred to as a:

A pathogen that can establish an infection in an otherwise healthy host is known as a primary pathogen. Primary pathogens possess the necessary virulence factors to bypass the host's immune defenses and initiate disease in healthy individuals. These pathogens are often associated with disease regardless of the host's immune status. Examples include well-known infectious agents such as the influenza virus, Mycobacterium tuberculosis, and Streptococcus pneumoniae.

In contrast, opportunistic pathogens typically cause infections in hosts with compromised immune systems, meaning they take advantage of a weakened state rather than attacking a healthy individual. Secondary pathogens usually refer to infections that follow or are a consequence of a primary infection. Chronic pathogens involve infections that persist over a long period, but they do not specifically define the ability to infect healthy hosts. Thus, the term that accurately describes a pathogen capable of infecting healthy individuals is indeed primary pathogen.