Herpes infections soar globally as new study reveals massive disease burden

Revealing a global crisis: Groundbreaking research highlights the immense health impact of HSV infections, calling for a shift toward vaccine innovation and prevention measures.

Study: Estimated global and regional incidence and prevalence of herpes simplex virus infections and genital ulcers in 2020: mathematical modeling analyzes. Image credit: sokolova_sv/Shutterstock

In a recent study published in the journal Sexually transmitted infectionsa group of researchers estimated the global and regional incidence and prevalence of genital herpes simplex virus (HSV) and associated genital ulcer disease (GUD) infections in 2020, disaggregated by World Organization region of Health (WHO), sex and type of HSV.

Background

HSV type 1 and type 2 cause lifelong infections with significant global prevalence, resulting in considerable health and economic burdens. Both types involve frequent subclinical shedding and symptomatic reactivations, negatively affecting quality of life, sexual health, and mental health, including depression and anxiety.

HSV-2 increases the risk of HIV acquisition and transmission threefold, demonstrating a synergistic relationship between the two infections. HSV-2 is transmitted primarily through sexual contact and is the leading cause of recurrent GUD. Neonatal herpes, which is transmitted at birth or through postnatal oral contact, has a high mortality rate and poses significant public health concerns.

HSV-1, usually acquired orally during childhood, can also cause serious complications, including neurological, corneal, and mucocutaneous conditions, and has become a major cause of genital herpes in high-income countries. Further research is essential to develop effective prevention and treatment strategies, including vaccines.

About the study

The study used data from systematic reviews and meta-analyses to provide model data, updated as of March 30, 2022, to ensure completeness for all WHO regions. Only data collected through 2020 were included, with country-level data reorganized into WHO regional groups.

The study also incorporated methodological improvements, including refined calibration techniques and updated prevalence data, to improve the accuracy of its estimates. The validity of HSV diagnostic tests has been evaluated to address limitations such as sensitivity, specificity, and cross-reactivity between HSV-1 and HSV-2 antibodies.

Studies using unreliable laboratory methods were excluded. To ensure accuracy, the tests needed to detect type-specific antibodies, such as glycoprotein G-2 for HSV-2.

Meta-analyses were performed using DerSimonian-Laird random effects models, and pooled prevalence estimates were stratified by sex and age. These estimates were used to calibrate a mathematical model based on the WHO HSV estimation framework. Calibration incorporated prevalence data using a constant incidence rate model while adjusting for demographic changes and sparse data in specific regions.

The study generated incidence and prevalence estimates of genital HSV-1 and HSV-2 infections in individuals aged 15 to 49 years and of oral HSV-1 infections in those 0 to 49 years of age. GUD estimates were derived by applying natural history parameters to infection estimates. Uncertainty intervals were calculated using Monte Carlo simulations.

Study results

HSV-2 remains the leading cause of genital infections and recurrent GUD. In 2020, the estimated number of new HSV-2 infections worldwide among individuals aged 15 to 49 years was 25.6 million (95% uncertainty interval (UI): 23.1 to 29.4 million), women representing 15.6 million cases and men 10.0 million.

The African region reported the highest incidence, contributing 38.3% of all infections. Incidence rates were significantly higher among young adults, particularly in Africa and the Americas. This reflects both demographic trends and different patterns of sexual behavior across regions.

The estimated global prevalence of HSV-2 in the same age group was 519.5 million cases (95% IU: 464.3 to 611.3 million), with higher prevalence among women (17, 0%, 95% UI: 14.9 to 20.1%) compared to men. (9.7%, 95% UI: 8.0-13.0%).

For genital HSV-1 infections, the number of new cases worldwide in 2020 among individuals aged 15 to 49 years was 16.8 million (95% UI: 10.6 to 22.4 million), distributed evenly between the sexes. The Western Pacific region recorded the highest incidence.

The global prevalence of genital HSV-1 infections in the same demographic group has been estimated at 376.2 million cases (95% UI: 235.6 to 483.5 million), with slightly higher prevalence among women. (10.5%, 95% UI: 6.4 to 13.8%) than in women. men (9.9%, 95% UI: 5.9-13.4%).

Overall, the combined global incidence of genital HSV infections (HSV-1 and HSV-2) among individuals aged 15 to 49 years was 42.4 million (95% IU: 33.7 to 51 .8 million), while the prevalence was 846.1 million (95% IU: 661.1-1034.2 million). The prevalence of GUD due to HSV-2 in this age group was 4.8% (95% UI: 3.0 to 7.5%), affecting approximately 187.9 million people, with women experiencing greater higher prevalence (6.2%, 95% UI: 3.8 to 9.6%). ) than men (3.5%, 95% UI: 2.2-5.8%).

For HSV-1, the prevalence of GUD was 0.5% (95% UI: 0.3-0.7%), affecting 16.7 million people worldwide. This translates to a combined GUD burden of 204.6 million people, with significant psychosocial and economic consequences. The total number of person-days with HSV-related GUD was estimated at 8.8 billion (95% UI: 5.8–15.4 billion).

For oral HSV-1 infections, the global prevalence in 2020 among individuals aged 0 to 49 years was 58.6% (95% UI: 53.5 to 62.1%), which is equivalent to approximately 3.4 billion people. The African region had the highest oral prevalence of HSV-1, while the Western Pacific region had the highest number of infected people.

Conclusions

To summarize, in 2020, 26 million people aged 15 to 49 acquired new HSV-2 infections, including 520 million living with HSV-2 and 188 million suffering from HSV-2-related GUD. Similarly, 17 million people acquired new genital HSV-1 infections, including 376 million living with genital HSV-1 and 17 million suffering from HSV-1-related GUD.

Despite advances in treatment, prevention efforts remain insufficient, highlighting the critical need for HSV vaccines to curb transmission and reduce the burden of disease. HSV-2 is primarily transmitted sexually, while HSV-1 is primarily acquired orally during childhood, although genital transmission is increasing. Genital infections with HSV-1 are less recurrent than those with HSV-2.