The word "psittacosis" is used when the disease is carried by any species of bird belonging to the family Psittacidae, whereas "ornithosis" is used when other birds carry the disease. In humans, after an incubation period of 5–19 days, the symptoms of the disease range from inapparent illness to systemic illness with severe pneumonia. It presents chiefly as an atypical pneumonia. Complications in the form of endocarditis, liver inflammation, inflammation of the heart's muscle, joint inflammation, keratoconjunctivitis (occasionally extranodal marginal zone lymphoma of the lacrimal gland/orbit), and neurologic complications (brain inflammation) may occasionally occur. . Most persons respond to oral therapy doxycycline, tetracycline hydrochloride, or chloramphenicol palmitate.