6. Fever
You are likely to get a fever when your body is fighting an infection. A fever is common when a person is infected with the syphilis. It usually occurs not long after secondary symptoms begin to appear. During this phase of illness, a person may feel quite weak and have a fever.
A temperature can be treated by anti-inflammatory drugs, but it will return until the syphilis has been eradicated. The body must maintain a constant temperature to keep the fever at bay. The blood flows much faster when the lymphatic system becomes fully active and the body is in full defense mode. The body will overheat. It can also affect other organs and their functions, which may make a person feel ill.