Table 1.

Case definitions

Stage/disease	Definition
HSV	Typical single or multiple genital ulcers from which HSV-1 or HSV-2 DNA is isolated using an in-house PCR.
Primary syphilis	Diagnosis requires the presence of a chancre on examination and microbiological confirmation of Treponema pallidum with any of the following: dark ground microscopy, PCR provided by the sexually transmitted bacteria reference laboratory, Health Protection Agency, London, or positive treponemal serology (as per national guidelines).16 Primary diagnoses to include dark-ground negative ulcers and initially negative serology, which becomes positive up to 3 months later with no sign of secondary disease.
Secondary syphilis	Defined as syphilis within the first 2 years of infection and characterised by both clinical and microbiological findings. Clinical findings include typical rash, condylomata lata, muco-cutaneous lesions, generalised lymphadenopathy, anterior uveitis, hepatitis and splenomegaly. Microbiological findings must include serological tests consistent with secondary disease and may, if available, include PCR of secondary lesions.16 If anogenital examination reveals persisting chancres, the case is still counted as secondary.
Other syphilis	Latent syphilis
	Positive serological tests in the absence of any symptom or sign. Classified as early within the first 2 years of infection and late thereafter.
	Symptomatic late syphilis
	Positive serology including a negative or low and unchanging RPR titre together with symptoms and clinical signs of cardiovascular or gummatous disease. Late disease with neurological involvement is classed as neurosyphilis.
Neurosyphilis	Any stage of disease with clinical neurological involvement* (including meningitis, cranial nerve palsies, parenchymatous general paresis, tabes dorsalis), serological findings consistent with the stage of disease and a relevant CSF abnormality (as per national guidelines).16
	NB: For analysis, cases with neurological involvement were counted as neurosyphilis not by stage.
Asymptomatic contact of syphilis	Patient reports sexual contact with a suspected or confirmed case of syphilis. Examination reveals no sign of disease and serological results (baseline, 6 weeks and 3 months after exposure) are not consistent with current infection.
Non-specific genital ulceration	Genital ulceration is present on examination, but no microbiological diagnosis is made. PCR for HSV is negative, DGM is negative, syphilis serology is not consistent with current infection and diagnostic T pallidum PCR (if performed) is negative.

^*Patients without neurological symptoms do not routinely undergo CSF examination at our centre.

CSF, cerebrospinal fluid; DGM, dark ground microscopy; HSV, herpes simplex virus; RPR, rapid plasma reagin.