Population-Based Incidence of Infectious Mononucleosis and Related Hospitalizations: 2010 Through 2021.

Objective: To determine whether the risks of infectious mononucleosis (IM) and serious IM outcomes are changing over time.

Patients and methods: Individuals with a diagnosis of IM and hospitalizations due to IM were identified among persons residing in an Upper Midwest region between January 1, 2010, and December 31, 2021, using the Rochester Epidemiology Project. Infectious mononucleosis rates were calculated assuming the entire population between 2010 and 2021 was at risk, and IM-associated hospitalization rates were calculated among everyone with a diagnosis of IM. Poisson regression was used to test trends and estimate incidence and hospitalization rate ratios.

Results: We identified 5334 individuals with IM; the overall IM rate was 60.60 per 100,000 person-years (95% CI, 58.98 to 62.25). Rates were highest in females, individuals of White race, those with non-Hispanic ethnicity, and individuals 15 to 19 years old (all P<.05). Infectious mononucleosis rates decreased significantly over time among all age groups (all tests for trend, P<.05). Overall, 234 individuals (4.3%) were hospitalized with IM (43.87 per 1000 persons with IM; 95% CI, 38.43 to 49.87), and hospitalization rates among those with IM increased over time (test for trend, P<.05). Individuals younger than 10 years, those 20 years or older, and individuals of Hispanic ethnicity had increased risk for IM-associated hospitalization (all adjusted P<.05).

Conclusion: Although rates of IM diagnosis have decreased over time, risk of hospitalization in individuals with IM has increased. Age and ethnicity increase the risk of hospitalization due to IM.