Age Patterns of HSV-2 Incidence and Prevalence in Two Ugandan Communities: A Catalytic Incidence Model Applied to Population-Based Seroprevalence Data

Abstract

Background: Herpes simplex virus type 2 (HSV-2) is an incurable sexually transmitted infection associated with increased risk of acquiring and transmitting human immunodeficiency virus (HIV). HSV-2 is highly prevalent in sub-Saharan Africa, but population-level estimates of incidence are sparse.

Methods: We measured HSV-2 prevalence from cross-sectional serological data among adults aged 18-49 years in 2 south-central Uganda communities (fishing, inland). We identified risk factors for seropositivity, then inferred age patterns of HSV-2 with a Bayesian catalytic model.

Results: HSV-2 prevalence was 53.6% (n = 975/1819; 95% confidence interval, 51.3%-55.9%). Prevalence increased with age, was higher in the fishing community, and among women, reaching 93.6% (95% credible interval, 90.2%-96.6%) by age 49 years. Factors associated with HSV-2 seropositivity included more lifetime sexual partners, HIV positive status, and lower education. HSV-2 incidence peakied at age 18 years for women and 19-20 years for men. HIV prevalence was up to 10-fold higher in HSV-2-positive individuals.

Conclusions: HSV-2 prevalence and incidence were extremely high, with most infections occurring in late adolescence. Interventions against HSV-2, such as future vaccines or therapeutics, must target young populations. Remarkably higher HIV prevalence among HSV-2-positive individuals underscores this population as a priority for HIV prevention.

Keywords: HSV-2; catalytic model; incidence; population-based study; prevalence.

Figure 1.

Comparison of human immunodeficiency virus (HIV) prevalence by age stratified by herpes simplex virus-2 (HSV-2) serostatus and sex. Bars show HIV prevalence in each age group, with lines showing 95% binomial confidence intervals.

Figure 2.

Herpes simplex virus-2 (HSV-2) prevalence by age in men and women in fishing and inland communities. The solid line depicts the maximum a posteriori estimate of prevalence by age, the surrounding shaded area shows the 95% credible interval. The points represent the HSV-2 prevalence by age observed in the Sexually Transmitted Infection Prevalence Study (STIPS) data, vertical error bars show 95% binomial confidence intervals for each data point.

Figure 3.

Modelled herpes simplex virus-2 (HSV-2) incidence per year by age in men and women in fishing and inland communities. The solid line depicts the maximum a posteriori estimate of prevalence by age, the surrounding shaded area shows the 95% credible interval.