Syphilis is a bacterial infection that is usually passed on through having sex with someone who is infected. It can also be passed from an infected mother to her unborn child and, in rare cases, can be caught through injecting drugs.
It is extremely rare to catch syphilis through a blood transfusion in the UK as blood donors are carefully screened.
Three stages of disease
Stage 1 (primary syphilis). Symptoms of syphilis begin with a painless but highly infectious sore on the genitals or sometimes around the mouth. If somebody else comes into close contact with the sore, typically during sexual contact, they can also become infected. The sore lasts two to six weeks before disappearing.
Stage 2 (secondary syphilis). Secondary symptoms, such as a skin rash and sore throat, then develop. These symptoms may disappear within a few weeks, after which you experience a latent (hidden) phase with no symptoms, which can last for years. After this, syphilis can progress to its third, most dangerous stage.
Stage 3 (tertiary syphilis). At this stage, it can cause serious damage to the body.
The primary and secondary stages are when you are most infectious to other people. In the latent phase (and usually around two years after becoming infected), syphilis cannot be passed onto others but can still cause symptoms. See Symptoms of syphilis for more information on the stages of the disease.
How common is it?
The number of diagnoses of syphilis has risen substantially in the past decade in the UK. Rates are highest among men who have sex with men.
However, syphilis still remains one of the less common sexually transmitted infections in the UK. Between 2007 and 2008, there was a slight decline in diagnoses in the UK.
Outlook
If diagnosed early, syphilis can be easily treated with antibiotics, usually penicillin injections (see Treating syphilis for more information).
However, if it is not treated, syphilis can progress to a more dangerous form of the disease and cause serious conditions such as stroke, paralysis, blindness or even death.