A person suffering from an infection in whom the symptoms and signs are so minimal that either there is no request for medical assistance or the doctor fails to make the diagnosis. The patient usually has partial immunity to the disease, but since the infecting organisms (pathogens) are of normal virulence, nonimmune contacts can be affected with the full manifestations of the illness. The period of infectivity is confined to the shortened duration of the illness (in contrast to a carrier, in whom the pathogen is present without necessarily causing any ill effects). Alternatively the subject has had the disease but retains some of the pathogens (e.g. in the throat or bowel) and so acts as a continuing reservoir of infection.