Cytomegalovirus seroprevalence and seroconversion in the Irish blood donor population.

Cytomegalovirus (CMV) is a ubiquitous virus with significant public health implications, including severe morbidity and mortality in neonates and immunosuppressed individuals. Substantial variation in CMV prevalence has been reported globally, and local epidemiological data are important to inform public health interventions. In this study, we estimated CMV seroprevalence and seroconversion rates among blood donors to provide baseline data on CMV epidemiology in Ireland. Seroprevalence was estimated in 74,821 donors, and seroconversion rates were calculated among returning donors, with associations assessed by demographic and geographical factors. Overall CMV seroprevalence in 2020 was 26.0% [95%CI: 25.7-26.3]. Female donors had higher odds of seropositivity than males (adjusted OR: 1.38, [95%CI: 1.34-1.43]). Among first-time donors, CMV seroprevalence was 23.82% [95% CI; 22.79-24.86], whereas within Sample Only New Donors (SOND), who are first-time donors born outside of Ireland and the UK, the seroprevalence was significantly higher, at 46.49% [95% CI; 40.41-52.98, p < 0.001]. The estimated annual seroconversion rate was 0.76% [95% CI: 0.68-0.85], with CMV DNA detected in 6.5% of seroconverters. These findings highlight a low CMV seroprevalence in Ireland, suggesting increased susceptibility to primary infection. Analysis of blood donor CMV data is a useful epidemiological tool to assess population-level risk.