After exposure, symptoms usually appear within three weeks. They usually present as non-specific lung problems which can easily be mistaken for influenza. Chronic forms of the disease can be mistaken for tuberculosis. A lung x-ray of a patient with the disease will look normal in about half of cases. There is an antibody test, but in most cases it is a false positive and only shows the person was exposed in the past. However, it will show up in blood cultures, sputem cultures and cultures taken from infected organs.