In medicine (pulmonology), psittacosis also known as parrot disease, parrot fever, and ornithosis is a zoonotic infectious disease caused by a bacterium called Chlamydophila psittaci (formerly Chlamydia psittaci) and contracted from parrots, such as macaws, cockatiels and budgerigars, and pigeons, sparrows, ducks, hens, gulls and many other species of bird. The incidence of infection in canaries and finches is believed to be lower than in psittacine birds. In certain contexts, the word 'psittacosis' is used when the disease is carried by any species of bird belonging to the Psittacidae family, whereas 'ornithosis' is used when other birds carry the disease. In humans, after an incubation period of 514 days, the symptoms of the disease range from inapparent illness to systemic illness with severe pneumonia. It presents chiefly as an atypical pneumonia.