Syphilis is a sexually transmitted infection, or STI.
Syphilis can be spread by having sex with an infected person, including oral and anal sex, and sharing sex toys.
In some cases, syphilis can be caught through close contact with the body of a person who has infected syphilis sores.
The syphilis bacterium Treponema pallidum cannot survive for long away from the body, so it can't be caught from using the same toilet, clothing or cutlery or bathroom as an infected person. Syphilis may be spread by injecting drug users sharing needles.
Pregnant women with syphilis can give it to their baby, with the risk of stillbirth.
Despite safer sex campaigns, 4,317 people were diagnosed with syphilis in England in 2014.
Syphilis infection occurs in three stages:
Stage 1: Primary syphilis
The first symptoms of syphilis are a painless but very infectious sore or ulcer known as a chancre, on the genitals or around the mouth. The infection is spread by contact with these sores, which last around two to six weeks. During this stage, a person may also experience swollen lymph glands, including those the neck, groin or armpit.
Stage 2: Secondary syphilis
The next stage of syphilis symptoms includes a non- itchy skin rash and sore throat lasting few several weeks. A person may also feel tired and experience headaches. Other symptoms include fever, weight loss, patches of hair loss and joint pain.
Picture: Secondary stage rash on the palms of the hands.
The primary and secondary stages are when there is a greater risk of passing the infection to other people.
This is followed by a hidden or latent stage where no symptoms are experienced. This can last for some years.
Stage 3: Tertiary syphilis
This third stage of syphilis is the most dangerous, affecting around a third of people who are not treated for syphilis in the earlier stages. Tertiary syphilis can cause damage to the brain, nerves, eyes, heart, bones, skin or blood vessels. This may lead to serious or even life-threatening conditions including stroke, heart disease, dementia, loss of co-ordination, numbness, paralysis or becoming blind or deaf.
People with syphilis are around three to five times more likely to be infected with HIV, which can enter the body through any syphilis sores that start to bleed during sex.
How is syphilis diagnosed?
A GP or doctor at a sexual health or genitourinary medicine (GUM) clinic will first examine the person's penis or vagina and anus for signs of syphilis. A blood test for syphilis antibodies and other STIs will be arranged.
A positive syphilis blood test result showing that antibodies the body uses to fight infection are present means a person has syphilis or had a previous syphilis infection.
A negative result does not always mean a person is clear of syphilis as it may take some months for antibodies to show up. Another test may be arranged after three months.
If the doctor sees sores, a swab of fluid will be taken for laboratory analysis.
A person's sexual partners should also be tested. A sexual health clinic will be able to help with confidential contact slips to help avoid embarrassment.
Syphilis blood tests are a routine part of antenatal screening for pregnant women.