Herpes is more common than you might think — way more common, actually. In 2020 alone, over 25 million people between the ages of 15 and 49 contracted a new genital infection with herpes simplex virus type 2 (HSV-2). Add to that another 17 million who acquired genital herpes from HSV-1, the same virus responsible for cold sores.

These figures add up every year because here’s the thing: herpes is a lifelong infection. You get it once, you always have it. Your immune system can usually keep it under control and get the virus to go dormant, but you can’t technically cure it. As a result, the number of people with herpes continues to grow. According to a new estimate, globally, nearly 850 million people now live with genital herpes — and almost 4 billion with cold sore herpes.

Silent but prevalent

The herpes simplex virus comes in two forms: HSV-1 and HSV-2. Traditionally, HSV-1 has been associated with oral infections (cold sores), while HSV-2 has been the primary culprit behind genital infections. However, changing sexual practices (particularly oral sex) means that HSV-1 is increasingly causing genital infections, particularly in higher-income regions.

Once contracted, the virus hides in nerve cells, periodically reactivating and causing painful sores or ulcers. These outbreaks can be distressing and disruptive, often accompanied by a sense of stigma and shame. The outbreaks are usually nothing more than a nuisance for adults, but in rare cases, they can be very dangerous for newborns, potentially even fatal.

Despite being such a widespread condition, herpes remains a largely neglected public health issue. That’s why Manale Harfouche, a researcher associated with the World Health Organization, carried attempted to estimate the number of people carrying the virus.

They used a calibrated mathematical model based on a systematic review and meta-analysis of herpes simplex virus (HSV) prevalence data across all World Health Organization (WHO) regions. Essentially this was a “study of studies,” where researchers tried to put together information from multiple previous research efforts. They zoomed in on the year 2020.

The researchers gathered data from 76,972 citations, narrowing it down to studies with valid laboratory methods for diagnosing HSV-1 and HSV-2. The model inputs included age- and sex-specific prevalence rates, categorized by region, and demographic data from the United Nations Population Division.

Over 4 billion people overall have herpes

HSV-1 is of less concern, although the sheer number of infections is staggering. Some 4 billion people have it, according to the estimate.

Researchers were more concerned with HSV-2, which is mostly sexually transmitted and has more frequent and painful outbreaks. Around half a billion (520 million) people aged 15 – 49 were living with the disease in 2020. For all ages, an estimated 1 in 5 people have HSV-2. Some people may never have experienced an outbreak and may not be aware that they have it.

For HSV-2, women are disproportionately affected, having almost double the infection rate of men. Women’s anatomy makes them more susceptible to genital herpes, and they may also face greater barriers to seeking treatment due to stigma.

The geographical burden of herpes is not evenly distributed. Sub-Saharan Africa bears the heaviest load. Nearly 10 million new HSV-2 infections occurred in this region in 2020, accounting for about 40% of all new cases globally. By age 50, many people in Africa have been infected with HSV-2 due to higher transmission rates and a lack of effective prevention measures.

The impact of HSV-2 in Africa is compounded by its interaction with HIV. Studies show that people with HSV-2 are at least three times more likely to acquire HIV. Given that both viruses are prevalent in this region, their synergy fuels a devastating public health crisis.

Current prevention isn’t enough

The researchers emphasize that new prevention and treatment measures such as prophylactic and therapeutic HSV vaccines “are needed critically to control HSV infections and reduce the associated disease burden.”

A herpes vaccine has long been the holy grail of prevention efforts. Researchers have made progress, but developing a safe and effective vaccine for herpes has proven difficult. The virus’s ability to hide in nerve cells and evade the immune system makes it very difficult to design an effective vaccine against it. Another problem is funding: herpes vaccines receive way less investments than other conditions.

Public awareness campaigns and education efforts have also made strides in promoting safer sex, but these measures alone are insufficient to curb the herpes epidemic. The study underscores the urgent need for new prevention tools, particularly vaccines.

Herpes isn’t the worst disease in the world by any means. But it’s incurable. While the physical symptoms of herpes are well-documented, the psychological effects are often ignored. A herpes diagnosis can be emotionally challenging, triggering anxiety, depression, and feelings of isolation. Many people fear rejection by their partners or face misconceptions about their sexual behavior. Because herpes can lead to stigma, it’s also rarely brought into discussion, both on a personal and a policy level.

Herpes is a global pandemic, but it doesn’t have to be a silent one. If we want to tackle it, we need a coordinated global response. Governments, health organizations, and researchers must prioritize herpes prevention, treatment, and vaccine development.

Manale Harfouche et al, Estimated global and regional incidence and prevalence of herpes simplex virus infections and genital ulcer disease in 2020: mathematical modelling analyses, Sexually Transmitted Infections (2024). DOI: 10.1136/sextrans-2024-056307