Genital herpes infections are very common. There are 42 million new infections each year — that averages out to one new person infected each second.
While treatments can help with symptoms, there's no cure. So once someone gets infected, they've got the virus for life. In the 15-to-49-year-old age range, 1 in 5 people are living with a genital herpes infection — that's about 846 million people.
These estimates were published this month in the journal Sexually Transmitted Infections.
"It is incredibly valuable [to have these new estimates], so that it is not the forgotten virus forever," says Dr. Keith Jerome, a professor of virology at the Fred Hutchinson Cancer Center who was not involved with the study. "We're talking about literally hundreds of millions of people living with these infections, I think it really reinforces the case that it's time to put some more effort into finding new and better therapies and treatments."
NPR spoke with one of the study authors: Laith Abu-Raddad, a professor of infectious disease epidemiology at the Qatar campus of Weill Cornell Medicine, to understand what's driving these huge numbers.
The first question
When talking about his work, Abu-Raddad says one of the first questions he's asked is whether case counts are going up or down.
The answer, he says, is not so simple. For starters, the methods used to make the estimations have changed a lot over the years as has the data the researchers are using in their analysis.
And then there's the fact that there are two types of herpes simplex virus that cause genital herpes – HSV-1 and HSV-2.
HSV-1 is less common as the source of genital herpes and typically shows up as oral herpes – mouth sores. HSV-2 is responsible for 90% of genital herpes episodes and is known to flare up over the years.
And their numbers are moving in opposite directions. Plus, rates of infection vary depending on where you look in the world. But before we get to that, let's look at the basics of infection.
How you get it
Both HSV-1 and HSV-2 spread through sexual contact. Since the HSV-1 virus can also cause an oral infection, it can spread through close contact like shared tableware, slobbery toys that kids share and kissing too.
Most of the time, these infections go unnoticed. That's because the majority of people have no symptoms or very few.
However, each year, about 20% of those infected with genital herpes – an unlucky 200 million people – have at least one outbreak where the virus causes painful genital sores and blisters.
A study from July of this year found that genital herpes costs $35 billion a year globally, between medical costs and lost economic productivity – for example, the blisters can be so uncomfortable that someone skips work.
"It can be very painful. Lots of itching, burning and sometimes there can be huge ulcers [lesions]," says Abu-Raddad. "But, a lot of the time, these ulcers are so small they are not visible [and not painful], but when we are swabbing people, most of the time we see very active virus."
HSV-1 …
So now, let's dive into the details.
Genital herpes caused by HSV-1 is growing more common in certain places, like Japan, Australia, the U.S., and Western Europe. In these places, fewer people are getting oral herpes infections and more getting genital herpes.
Why is that?
"What we are seeing, especially in developed countries, is less and less people are getting HSV-1 in childhood because of improved hygiene – people are less likely to share, say, utensils, family size is lower so they are less likely to get it by playing with their siblings," Abu-Raddad explains. "So more and more people are reaching sexual debut without getting infected by HSV-1 orally."
The bad news is that this lack of childhood exposure puts them at risk of genital infection by HSV-1.
When it comes to genital herpes from HSV-1 "oral sex is usually the mode of transmission," he says. "Someone with the ulcers in their mouth will be having sex with someone who never got infected as a child, so they will pass the virus to the genital area."
Abu-Raddad says his team sees a particular uptick in genital HSV-1 herpes as people enter college "because this is usually when they start serious sexual activity in their life."
The growing prevalence of genital herpes from HSV-1 is a decades-long trend that's been documented in various studies. One study called this transformation "remarkable," finding that in the U.S. in 1970 there were roughly 252,000 new genital HSV-1 infections. Fast forward to 2018 and the new infections that year had nearly doubled, to 410,000. The percent of the total U.S. population impacted increased 4.5% to 5.4% in that time period.
And what about HSV-2?
HSV-2 is the bigger beast of the two because of its ability to periodically reactivate, causing painful new outbreaks. For some, these outbreaks can surface through their whole lifetime, often triggered by a weakened immune system.
But there is some encouraging data. In sub-Saharan Africa – where HSV-2 is most common – the rate is dropping at a "substantial" clip, says Abu-Raddad. In the early 1980s, about half of the population had HSV-2 but, now, it's around a third of the population.
And HIV plays a role – in bringing numbers down.
This might sound counterintuitive because an HSV-2 infection actually puts you at a higher risk of contracting HIV, doubling or even tripling your risk. "These ulcerations basically create an opening gate for HIV to enter. Also these ulcerations, when they happen, there are more immune cells [present in the area] and these immune cells are the target cells for HIV," says Abu-Raddad.
But the rate is dropping in large part because of the response to the HIV epidemic that hit sub-Saharan Africa.
"Following the AIDS epidemic, there were lots of interventions – so people started using condoms more often, for example," he says, explaining that condoms lower the chance of spreading genital herpes. It's this type of education and prevention strategies that have helped reduce HSV-2 rates.
There's also another sad explanation for the drop: "Lots of people died of AIDS," Abu-Raddad explains, adding that those with risky sexual behavior – who were more likely to have and spread HSV-2 – were also the people most likely to die because of AIDS. Tragically, their deaths from AIDS means fewer people alive with HSV-2 and fewer people spreading it.
What can the world do?
Unlike high-profile viruses, genital herpes rarely gets attention — and research funding, Abu-Raddad says.
"People who suffer from genital herpes are unlikely to go public and say, 'Well, I'm suffering from genital herpes.' So it's not visible," he says. Plus, except for rare cases of neonatal herpes, it's unlikely to be fatal. "And, so, we have done very little to reduce it."
The main drug used against genital herpes is Acyclovir, which was one of the first antivirals developed in the 1950s by Gertrude Elion who won the Nobel Prize for her work. "And still today, for herpes, we're largely operating with a 70-year-old drug," says Dr. Jerome of the Fred Hutchinson Cancer Center. "And meanwhile, you've seen so many new antivirals for HIV, for hepatitis C, for hepatitis B, for COVID, which says something."
Both men hope the new numbers on genital herpes – and the story behind them – help alert the public and motivate work on therapeutics and vaccines.
"It's time to do something about it," Abu-Raddad says.
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