Around one in every five people aged below 50 around the world is infected with incurable genital herpes, researchers have newly estimated.
According to a new paper in the journal Sexually Transmitted Infections, 846 million people worldwide are genitally infected with the herpes simplex virus—which causes both genital and oral herpes—with 42 million new cases in 2020 alone.
During the same year, the researchers predict that over 200 million 15 to 49-year-olds likely had at least one outbreak of the infection.
This marks an increase in estimated cases from previous years, indicating that the development of new treatments and vaccines is urgently needed.
"Herpes simplex virus (HSV) type 1 and type 2 infections are lifelong, globally prevalent, and cause a significant disease burden, including symptomatic genital ulcer disease (GUD), and economic costs," the researchers wrote in the paper.
There are two forms of herpes simplex virus, HSV-1 and HSV-2, both spread via skin-to-skin contact. HSV-1 primarily causes oral herpes, while HSV-2 usually causes genital herpes, though both types can cause infection in both locations.
HSV infections are incurable, establishing a latent infection in nerve cells, and can cause occasional flare-ups of painful blisters or sores. Around the mouth, these are often known as cold sores, or genital ulcer disease when around the genitals.
"In addition to the painful genital sores, genital herpes is associated with a range of social and psychological adverse outcomes, including effects on sexual relations, quality of life, and mental health issues such as depression, anxiety, and low self-esteem," the researchers wrote.
According to the paper, the number of people aged 15–49 years with genital infections from HSV-2 or HSV-1 worldwide in 2020 was 846.1 million. Some 520 million of these are thought to be due to HSV-2, with 26 million new cases of HSV-2 being recorded in 2020. Of these new cases, 15.6 million were female and 10 million were male.
Around 4 billion people worldwide—two-thirds of the global population—are thought to be infected with HSV-1, the majority of which only have the oral form of the infection. However, in 2020, 376 million 15–49 year olds had the genital form of HSV-1, and 17 million new people were infected that year.
Genital herpes is spread via sexual contact, with infection being most likely if someone has sores and is experiencing a flare-up. HSV-2 tends to shed more frequently than HSV-1 in the genital area, and people who recently acquired the infection are more likely to experience shedding than those who have had the virus for a long time.
After infection from HSV, many people never develop symptoms. However, others may experience severe pain from the sores, especially during the first outbreak. The virus never goes away, lying dormant in the nerve cells, and may occasionally reactivate and cause recurrent sores. These flare-ups may be triggered by illness, stress, injuries, sun exposure, or even menstruation.
The researchers also found that about 188 million people with HSV-2 and 17 million people with HSV-1 had at least one episode of genital sores in 2020 alone.
During periods where a flare-up is not occurring, the virus isn't usually transmissible, although asymptomatic shedding can occur periodically in both HSV-1 and HSV-2 infections, even in people who have no visible outbreaks.
Daily suppressive therapy with antivirals can reduce the frequency of asymptomatic shedding, lower the risk of transmission, and also prevent flare-ups of sores. However, they cannot completely clear the virus from the body.
This study shows that huge numbers of people around the world are infected with herpes. In the U.S., herpes infections are also incredibly prevalent: CDC data shows that there were 572,000 new genital herpes infections in the U.S. in 2018 alone.
In 2023, the CDC recorded 209,000 cases of syphilis, 600,000 cases of gonorrhea, and over 1.6 million cases of chlamydia.
The researchers note that therefore there is a widespread need for more sophisticated treatment for HSV, as it affects so many and has such a large stigma attached to it.
"Available prevention modalities, including condoms and antiviral therapy, are insufficient to control infection transmission and have, at best, had a modest population impact in reducing incidence rates," the researchers wrote.
"There is a need for HSV prophylactic and therapeutic vaccines as a strategic approach to control transmission and to curb the disease and economic burdens of these infections."
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References
Harfouche M, AlMukdad S, Alareeki A, et al. (2024) Sex Transm Infect. doi:10.1136/sextrans-2024-056307