Whether a condition counts as a sexually transmitted infection decides what enters surveillance, what gets programme funding, and what appears on a screening panel. There is no agreed operational classification linking the working definitions to those decisions, and microbiology, clinical medicine and public health each draw the boundary in a different place.
The authors of this Personal View argue that the contested cases expose the problem: bacterial vaginosis, vulvovaginal candidiasis, scabies, mpox and sexually transmissible enteric pathogens all sit awkwardly inside a yes-or-no category. They propose three tiers — core sexually transmitted infections, sexually associated infections, and incidental sexually transmissible infections — anchored on four explicit classification dimensions, with conditions able to move between tiers as evidence and local epidemiology change.
They also raise what a formal classification could cost. Naming a condition as sexually transmitted changes how patients are treated by services and by each other, and the equity and stigma consequences fall unevenly. For a clinician the immediate use is in how you explain a diagnosis: bacterial vaginosis is the common example where the label a patient hears determines whether a partner is blamed, and a graded vocabulary is more honest than forcing one.
- Be precise in the notes about whether an infection is sexually transmitted, sexually associated, or incidentally transmissible
- Choose the words you use with the patient deliberately — bacterial vaginosis is the recurring example
- Check what your local screening panel actually covers, which is a programme decision rather than a clinical one
- Expect surveillance definitions to lag any change in classification
- Note this is a proposal under discussion, not a standard anyone is currently applying
Why it matters
The category boundary, not the clinical need, currently decides what gets tested for and funded.
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