Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema, subspecies pallidum (Treponema Pallidum). The primary route of transmission is through sexual contact (vaginal or anal); however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis. Syphilis is particularly common in developing countries, agmong commercial sex works and among MSMs.
Its symptoms and signs of syphilis vary widely depending on which of the 4 stages of the disease (primary, secondary, latent or tertiary). In primary syphilis, it typically presents with a chancre (a firm, painless, non-itchy ulcer) which can be on the penis, outside the anus, on labia and even inside the vagina or rectum. Because it is painless and non-itchy, therefore it is quite easy to miss. Without treatment, the chancre will disappear by itself in about 1-2 weeks.
Then syphilis goes into an asymptomatic period which can last for months. In secondary phase, a rash may appear on the body, hand or feet. But the rash is again non-itchy and non-painful, therefore again can be easily missed. Quite often the patients or even doctors may think it is just an allergy and dismiss it. The rash typically last for about 2 weeks and will disappear again.
The infection then enter a very long latent phase without symptom. However, syphilis is usually only infectious in the first 6 months. The infection stay within the infected person without symptom for many years and later develops into tertiary syphilis which can affect major organs such as the brain and heart and causing permanent damage. The most common form of tertiary syphilis is call gummatous syphilis which the person will develop inflammatory nodules on skin, bone, brain or other parts of the body. In about 6-10% of patients may develop neuro-syphilis (affecting central nervous system) or cardiovascular syphilis (commonly causing aortic aneurysm).
During its asymptomatic stages it can only be detected through regular blood tests. If syphilis is treated early, not only it can be eradicated much easier, it also help to reduce the chance of spreading the infection.