The epidemiology of infectious mononucleosis in Northern Scotland: a decreasing incidence and winter peak

BACKGROUND: Infection with Epstein-Barr virus (EBV) is almost ubiquitous in humans and generally occurs at two ages: infantile, which is usually asymptomatic and associated with poorer socioeconomic conditions, and adolescent, which causes infectious mononucleosis (IM) in ~25% cases. The determinants of whether the infection causes IM remain uncertain. We aimed to evaluate seasonality and temporal trends in IM. METHODS: Data from all Monospot tests, used as a marker for IM, were collected from the Grampian population over 16 years. RESULTS: Positive Monospot test results peaked at 17 years in females and 19 in males. Females had 16% more diagnoses, although 55% more tests. IM was ~38% more common in winter than summer. The annual rate of positive tests decreased progressively over the study period, from 174/100 000 (95% CI 171–178) in 1997 to 67/100 000 (95% CI 65–69) in 2012. CONCLUSIONS: IM appears to be decreasing in incidence, which may be caused by changing environmental influences on immune systems. One such factor may be exposure to sunlight. Words 168. Funding The Medical Research Council and NHS Grampian-MS endowments.