Pre-symptomatic asymptomatic MonkEypox (PRIME) study

The aim is to improve understanding of monkeypox (MPX) transmission by identifying the proportion of sexual contacts of MPX cases in whom MPX virus can be detected and the timing of detection in relation to any associated symptoms, to inform intervention strategies and modelling of disease spread. In this prospective cohort study, identified sexual contacts of confirmed MPX cases as well as individuals who self-report sexual contact with a confirmed MPX case will be asked to undertake self-sampling of nose and throat swabs, ano-genital swabs, and or urine samples depending on participant characteristics and the nature of sexual contact with the index case. Optional serologic testing will be performed by self-sampling at baseline and one month after the last exposure to a MPX case. Informed consent will be obtained and all results will be fed back to individual participants. The primary objective is to estimate the proportion of secondary MPX cases who develop pre-symptomatic or asymptomatic MPX infection, defined as detectable viral DNA at any body site before the onset of symptoms or in the absence of symptoms, respectively. This will be achieved by PCR testing of swabs from nose and throat swabs, ano-genital swabs and/or urine tests at two intervals until 21 days following last sexual exposure with a confirmed MPX case, and optional serology testing at baseline and one month after the end of the first participants' exposure to a MPX case. Secondary objectives are to: a) Estimate the secondary attack rate (SAR) of MPX infection in a defined cohort of known sexual contacts of confirmed cases. SAR is defined as the proportion of sexual contacts of MPX cases who have detectable viral DNA at any body site and/or seropositivity b) Estimate the vaccine effectiveness (VE) of smallpox vaccination for asymptomatic infection c) Estimate the incubation period before development of, and the duration of, asymptomatic and pre-symptomatic viral shedding