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. 2025 Jul 11;231(6):e1151-e1159.
doi: 10.1093/infdis/jiaf157.

Age-Dependent Assortativeness in Herpes Simplex Virus Type 1 Oral Transmission in the United States: A Mathematical Modeling Analysis

Affiliations

Age-Dependent Assortativeness in Herpes Simplex Virus Type 1 Oral Transmission in the United States: A Mathematical Modeling Analysis

Hassan Hachem et al. J Infect Dis. .

Abstract

Background: Herpes simplex virus type 1 (HSV-1) is a highly infectious, globally prevalent lifelong infection. Despite advancements in understanding its epidemiology, the assortativeness in the age-dependent transmission patterns remains unclear. This study aimed to estimate the degree of assortativeness in age group mixing for oral-to-oral HSV-1 transmission within the United States (US) population.

Methods: An age-structured mathematical model was employed to describe HSV-1 transmission dynamics in the US population, incorporating its different modes of transmission. The model was fitted to nationally representative HSV-1 data from the National Health and Nutrition Examination Survey (NHANES) spanning 1976-2016 using a Bayesian inference framework. The degree of assortativeness in age group mixing was calibrated on a scale from 0 (no age group bias in close-proximity interactions) to 1 (exclusive mixing within the same age group).

Results: The model demonstrated robust fits to US demographics, age-specific HSV-1 prevalence, and temporal trends in both HSV-1 prevalence and ever-symptomatic HSV-1 genital herpes prevalence. The degree of assortativeness was estimated as 0.87 (95% credible interval [CrI], .64-.99) for children, indicating strong age-based assortativity, and as 0.04 (95% CrI, .004-.10) for adults, indicating weak age-based assortativity.

Conclusions: Most HSV-1 infections among children are acquired from peers within their own age group, whereas adults acquire HSV-1 infections from a broad range of age groups.

Keywords: Bayesian framework; assortativeness; genital herpes; mathematical model; oral herpes.

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Conflict of interest statement

Potential conflicts of interest. All authors: No reported conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

Figures

Figure 1.
Figure 1.
Fitting of age-specific herpes simplex virus type 1 (HSV-1) prevalence for each National Health and Nutrition Examination Survey (NHANES) round. Comparison of the model-fitted HSV-1 prevalence for each 5-year age band in the United States with NHANES data from 1976 to 2016. Abbreviations: CI, confidence interval; HSV-1, herpes simplex virus type 1; NHANES, National Health and Nutrition Examination Survey.
Figure 2.
Figure 2.
Fitting of herpes simplex virus type 1 (HSV-1) prevalence temporal evolution. A, Comparison of the model-fitted temporal trends in HSV-1 prevalence among individuals aged 10–49 years in the United States (US) with National Health and Nutrition Examination Survey (NHANES) data. B, Comparison of the model-fitted temporal trends in ever-symptomatic HSV-1 genital herpes prevalence among individuals aged 20–49 years in the US with NHANES data. Abbreviations: CI, confidence interval; HSV-1, herpes simplex virus type 1; NHANES, National Health and Nutrition Examination Survey.
Figure 3.
Figure 3.
Degree of assortativeness in herpes simplex virus type 1 infection transmission among children and adults. A, Model-estimated distribution of the degree of assortativeness among children aged 0–14 years. B, Model-estimated distribution of the degree of assortativeness among adults aged 15–99 years. C, Model-estimated mean and 95% credible interval (CrI) for the degree of assortativeness among children and adults.

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