A study estimating the number of under-50s worldwide who are living with genital herpes has highlighted changing sexual behaviors and the need for many countries to consider more effective ways of curbing the transmission of this incurable disease.

Infection with the herpes simplex virus (HSV) is for life. Although HSV-2 is the main cause of genital herpes, HSV-1 – the virus responsible for cold sores – can be transmitted by oral sex, so it, too, can also cause the condition. Most HSV infections are asymptomatic or have very mild symptoms. Still, some people experience recurrent outbreaks of painful genital blisters, which negatively affect sexual relations, quality of life, mental health, and self-esteem.

A team of international researchers has used a mathematical model to estimate the worldwide number of new and existing cases of genital herpes in people aged 15 to 49.

“In response to the clinical disease burden of these two infections and their impact on sexual and reproductive health and HIV transmission, the [World Health Organization] has advocated for efforts to reduce HSV disease burden by advancing the development of new prevention and treatment measures, such as vaccines,” said the researchers.

The present study provides an update on previous estimates of the global and regional incidence (new cases) and prevalence (existing ones) of HSV-1 and HSV-2 in 2012 and 2016. In addition to estimates of genital HSV infections for 2020, it also includes estimates for HSV-related genital ulcer disease (GUD), which is exactly what it sounds like. The term ‘region’ here refers to the World Health Organization’s (WHO) division of countries.

“In 2020, we estimated that 26 million people aged 15–49 years acquired a new HSV-2 infection, 520 million people were living with an HSV-2 infection, and 188 million people had at least one episode of GUD caused by HSV-2,” the researchers said. “Additionally, in 2020, 17 million people aged 15–49 years acquired a new genital HSV-1 infection through sexual transmission, 376 million people were living with genital HSV-1 infection, and 17 million people had at least one episode of GUD caused by HSV-1,” said the researchers.

So, how did the most recent estimates compare to those of 2016?

“HSV-2 global prevalence was virtually equal in the 2016 and 2020 estimation rounds,” the researchers said. “Considering the shifts in the underlying demography during this time (increase in the global average age and the changing proportion of the global population in each region), HSV-2 prevalence, adjusted for the demographic trends, appears to be slowly declining … This decline may reflect less risky sexual behavior following the HIV epidemic, improved sexually transmitted infection (STI) awareness, increasing access to HIV/STI services.”

However, the researchers saw a change in the data on genital HSV-1 infections.

“The estimated number of prevalent genital HSV-1 infections is nearly twofold higher in 2020 compared with 2016 (376 vs 192 million),” said the researchers. “[Analyses have] indicated increasing rates of genital HSV-1 infection and decreasing rates of oral infections in several regions, suggesting an epidemiological transition for this infection from an oral to increasingly genital acquisition.”

This finding suggests that transmission dynamics are changing, most probably because of a shift in sexual behavior, such as an increase in oral sex. An alternative explanation could be that exposure to HSV-1 during childhood has decreased in many regions due to improved hygiene or living conditions, which may mean that fewer people acquire the virus orally at a young age, leaving them susceptible to acquiring it later through sexual activity.

At present, even in resource-rich countries, there are very few specific programs targeting HSV prevention and control. The researchers hope that their findings will prompt a change.

“Available prevention modalities, including condoms and antiviral therapy, as insufficient to control infection transmission and have, at best, had a modest population impact in reducing incidence rates,” the researchers said. “There is a need for HSV prophylaxis and therapeutic vaccines as a strategic approach to control transmission and to curb the disease and economic burdens of these infections.”

The study was published in the journal Sexually Transmitted Infections.

Source: BMJ Group