Syphilis. Skin lesions on the shoulder of a man with secondary syphilis. Syphilis is an infection by the Treponema pallidum bacterium. The secondary stage of this disease usually starts about a month after the initial infection. It involves this rash and also headaches, pain in the bones and fatigue. This eventually subsides, and the patient appears normal. The latent stage may last for years, even decades, but can progress to tertiary syphilis with tissue death, blood vessel disease and paralysis by brain damage. All stages are treated with penicillin antibiotic drugs. The disease is usually transmitted during sex. Photographed in Africa.