Epidemiology

The annual incidence of IM in the US is estimated at 500 cases per 100,000 population, and people ages 15 to 24 years are the most affected age group. Approximately 10% to 20% of susceptible people become infected with Epstein-Barr virus (EBV) each year, and IM develops in 30% to 50% of these people.[11]

Seroprevalence studies from different countries consistently indicate past EBV infection in over 90% of adults by the age of 40 years.[12][13][14]

Data from a seroepidemiologic survey in the UK found that 85% of people aged ≤25 years were EBV positive. EBV seropositivity increased more rapidly in females compared with males during adolescence (ages 10-15 years). The incidence of IM increased between the years 2002 and 2013.[15] A seroprevalence study in younger people in England found that EBV infection was present in over half the population by the age of 11 years. Seroprevalence increased from 60.4% in 11-14 year olds, to 68.6% in 15-18 year olds, and to 93% in 22-24 year olds. Non-white ethnicity and smoking were also associated with increased EBV seroprevalence in this population.[16] In children and adolescents ages 6-19 years of age in the US, overall seroprevalence was 66.5%, and the rate increased with age from 54.1% in 6-8 year olds to 82.9% in 18-19 year olds.[17]

In developing countries, most children acquire EBV by the age of 4 years.[18] In developed countries, primary EBV infection tends to occur later in life. It is estimated that 30% to 75% of college freshmen are seronegative for EVB.[19] Epidemiologic data from developed and some developing countries indicate continuing shift of primary EBV infection to older patients, causing higher rates of severe infection in adolescents and adults.[20]

Outbreaks of IM are not common, probably the result of low efficiency of EBV transmission. The incubation period of IM is estimated at 30 to 50 days, but it is probably shorter in young children. No strong racial or sex predilection exists. No seasonality in IM incidence has been shown.

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