A woman in bed and a man sitting on a stool are covered with lesions from a venereal disease such as syphilis, which produces skin pustules; a physician standing next to the bed is holding up a urine flask for analysis; another physician is applying a salve to the man's legs. Woodcut by Bartholomaeus Steber, from c. 1497. Syphilis is caused by infection by the Treponema pallidum bacterium. The first European syphilis epidemics occurred in 1494. It is thought that it was introduced from the newly-discovered Americas or was a new, virulent form of another disease.