Virus causing genital herpes may put millions of people at greater risk of infection with HIV
About half a billion people worldwide are living with genital herpes, and several billion have an oral herpes infection, new estimates show.
Authored by staff at the University of Bristol, World Health Organization (WHO), and Weill Cornell Medical College-Qatar, and published in the Bulletin of the World Health Organization, the new study estimates the global infection prevalence and incidence of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) in 2016.
“Herpes infection affects millions of people across the globe and can have far-reaching health effects. We need more investment and commitment to develop better treatment and prevention tools for this infection.” says Dr Sami Gottlieb, Medical Officer at WHO and an author of the study.
Prevalence and incidence
An estimated 491.5 million people were living with HSV-2 infection in 2016, equivalent to 13.2% of the world’s population aged 15 to 49 years. HSV-2 is almost exclusively sexually transmitted, causing infection in the genital or anal area (genital herpes).
An estimated 3.7 billion people had HSV-1 infection during the same year – around 66.6% of the world’s population aged 0 to 49. HSV-1 is mainly transmitted by oral to oral contact to cause infection in or around the mouth (oral herpes). However, HSV-1 can also be transmitted to the genital area through oral-genital contact – during oral sex – to cause genital herpes. Most HSV-1 infections were oral; however, between 122 million to 192 million people were estimated to have genital HSV-1 infection, depending on the assumptions used in the estimation model.
Because herpes is a lifelong infection, estimated prevalence increased with age; HSV-2 prevalence was also higher among women and in the WHO African Region.
Health and social impacts
Most people living with herpes, caused by either HSV-1 or 2, are unaware they have the infection.
When symptoms do occur however, oral herpes infection can lead to painful sores around the mouth (“cold sores”). Genital herpes infection can cause recurring, often painful, genital sores, often referred to as genital ulcer disease.
WHO and partners published a study in March 2020 estimating that around 5% of the world’s population (187 million people) suffered from at least one episode of herpes-related genital ulcer disease in 2016 (1). Most of these episodes were due to HSV-2, which can recur frequently over many years.
Recurrent symptoms of genital herpes can lead to stigma and psychological distress, and can have an important impact on quality of life and sexual relationships. However, in time, most people with herpes adjust to living with the infection.
“Genital herpes is a substantial health concern worldwide – beyond the potential pain and discomfort suffered by people living with the infection, the associated social consequences can have a profound effect on sexual and reproductive health” says Dr Ian Askew, Director of the Department of Sexual and Reproductive Health and Research at WHO.
Herpes and HIV
A strong association exists between HSV-2 infection and HIV infection. In 2019, WHO commissioned a modeling study to estimate how much HSV-2 infection might contribute to HIV incidence. The study estimated that almost 30% of new sexually acquired HIV infections in 2016 worldwide were likely attributable to HSV-2 infection (2).
Evidence shows that people with HSV-2 infection are at least three times more likely to become infected with HIV, if exposed. HSV-2 leads to inflammation and small breaks in the genital and anal skin that can make it easier for HIV to cause infection. In addition, people with both HIV and HSV-2 infection are more likely to spread HIV to others.
Women have higher biologic susceptibility to both HSV-2 and HIV. Women living in the WHO Africa Region have the highest HSV-2 prevalence and exposure to HIV – putting them at greatest risk of HIV infection, with negative implications for their health and well-being.
For people living with HIV (or who are living with other conditions that compromise their immune systems) as well as HSV-2, the symptoms of herpes can be more severe and more frequent.
Neonatal herpes can occur when an infant is exposed to HSV in the genital tract during delivery. This is a rare condition, occurring in an estimated 10 out of every 100,000 births globally, but can lead to lasting neurologic disability or death. The risk for neonatal herpes is greatest when a mother acquires HSV infection for the first time in late pregnancy. Women who have genital herpes before they become pregnant are at very low risk of transmitting HSV to their infants.
No cure – better treatment and prevention needed
There is no cure for herpes. At present, antiviral medications, such as acyclovir, famciclovir, and valacyclovir, can help to reduce the severity and frequency of symptoms but cannot cure the infection.
As well as increasing awareness about HSV infection and its symptoms, improved access to antiviral medications and heightened HIV prevention efforts for those with genital HSV symptoms are needed globally.
In addition, development of better treatment and prevention interventions is needed, particularly HSV vaccines. WHO and partners are working to accelerate research to develop new strategies for prevention and control of HSV infections. Such research includes the development of HSV vaccines and topical microbicides. Several candidate vaccines and microbicides are currently being studied.
“A vaccine against HSV infection would not only help to promote and protect the health and well-being of millions of people, particularly women, worldwide – it could also potentially have an impact on slowing the spread of HIV, if developed and provided alongside other HIV prevention strategies” says Dr Meg Doherty, Director of the WHO Department of Global HIV, Hepatitis, and STI Programmes.