At least 1 person each second – 42 million people annually – is estimated to acquire a new genital herpes infection.

Most of the time, these infections cause no or few symptoms. However, for some people they lead to painful genital sores and blisters that can recur throughout life, causing significant discomfort and often requiring multiple healthcare visits.

According to the estimates, more than 200 million people aged 15 to 49 suffered at least one such symptomatic episode in 2020.

The authors of the study, published in the journal Sexually Transmitted Infections, say that new treatments and vaccines are needed to reduce adverse health effects of the herpes virus and control its spread.

“While most people with a genital herpes infection experience few symptoms, with so many infections genital herpes still causes pain and distress for millions globally and strains already overburdened health systems,” said Dr Meg Doherty, Director of Global HIV, Hepatitis and Sexually Transmitted Infections Programmes at WHO. “Better prevention and treatment options are urgently needed to reduce herpes transmission and will also contribute to reducing the transmission of HIV.”

Currently, there is no cure for herpes, although treatments can relieve symptoms.

In addition to sores, genital herpes can also on occasion lead to serious complications, including neonatal herpes – a rare condition most likely to occur when a mother acquires the infection for the first time in late pregnancy and then transmits the virus to her baby during childbirth.

There are two types of the herpes simplex virus (HSV), known as HSV-1 and HSV-2, both of which can lead to genital herpes. According to the estimates, 520 million people in 2020 had genital HSV-2, which is transmitted during sexual activity.

From a public health perspective, genital HSV-2 is more serious since it is substantially more likely to cause recurrent outbreaks, accounts for around 90% of symptomatic episodes, and is linked to a three-fold increased risk of getting HIV.

Unlike HSV-2, HSV-1 primarily spreads during childhood through saliva or skin to skin contact around the mouth to cause oral herpes, with cold sores or mouth ulcers the most common symptoms.

In those without previous infection, however, HSV-1 can be acquired through sexual contact to cause genital infection in adolescence or adulthood.

Some 376 million people are estimated to have had genital HSV-1 infections in 2020. Of these, 50 million are estimated also to have HSV-2 as it is possible to have both types at the same time.

While the 2020 estimates show virtually no difference in the prevalence of genital HSV-2 compared to 2016, estimated genital HSV-1 infections are higher.

Over recent years, several countries have observed changing patterns of transmission in HSV-1, with adult genital infections increasing as childhood oral infections decline.

Reduced oral spread during childhood may be linked to factors like less crowded living conditions and improved hygiene, which then increases susceptibility to the virus at older ages.

The authors note that these increases may also partially reflect changes in methods and additional data sources.

“Stigma around genital herpes means it has been discussed too little, despite affecting millions of people globally. Not enough has been done to address this common infection,” said Dr Sami Gottlieb, an author of the report and Medical Officer within WHO’s Department of Sexual and Reproductive Health and Research including the UNDP/UNFPA/UNICEF/WHO/World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP).

“Expanded research and investment in developing new herpes vaccines and therapies, and their equitable use, could play a critical role in improving quality of life for people around the world.”

While they are not fully effective at stopping its spread, correct and consistent use of condoms reduces risks of herpes transmission.

People with active symptoms should avoid sexual contact with other people, since herpes is most contagious when sores are present.

WHO recommends that people with symptoms of genital herpes should be offered HIV testing and if needed, pre-exposure prophylaxis for HIV prevention.