Syphilis

Syphilis is caused by the spirochete bacterium Treponema pallidum and progresses in stages. Primary syphilis produces a single painless sore (chancre) at the site of infection that heals on its own — a feature that leads many people to assume the problem resolved. Secondary syphilis follows weeks later with a rash that classically involves the palms and soles, fever, sore throat and swollen lymph nodes. After that the infection enters a latent stage with no symptoms, which can persist for years before tertiary complications affecting the heart, brain and nervous system. Diagnosis is by blood test, combining a treponemal test (which stays positive for life after infection) with a non-treponemal test such as RPR or VDRL (whose titre falls with successful treatment). Reading the two together is what distinguishes active infection from a treated past one — a point that matters if you have ever had a positive result before. Treatment is benzathine penicillin, highly effective in the early stages. Syphilis rates have risen sharply in many countries over the past decade, and congenital syphilis — transmission in pregnancy, which can cause stillbirth and severe neonatal disease — is the reason antenatal screening is near-universal.