We have a lethal virus carried by 0.2% of the community. It is sexually transmissible and the only preventive measures are behavioural; it is treatable but not curable. Should we screen for it, and if so, how often? No prizes for guessing that this a real question about HIV in the UK. The prevalence statistic is roughly similar to some parts of the USA, where this modelling study was conducted, and the cost-benefit equation is borderline (£15-30K per QALY) however you play the assumptions. The authors plump for screening.