Of the 8 billion people who inhabit our planet, nearly 1 billion of them have a painful infection that’s existed since the antiquities but still has no cure: herpes.

Herpes simplex virus, or HSV-1, mostly causes oral infection in the form of cold sores. HSV-2 causes genital ulcers. Both are contagious.

The World Health Organization research used sophisticated mathematical modeling to find that in 2020, roughly 846 million people between the ages of 15 and 49 carry the herpes virus. That age range is generally when adults tend to be most sexually active.

The researchers said the surprisingly high numbers suggest far more must be done to help stop the virus’ spread. Vaccines are needed. So is better treatment.

Despite the virus having been around for centuries, we don’t talk about it much. The stigma is enough to keep many affected by the virus from discussing it. There is often reluctance to be tested or even to date.

While its symptoms can be obvious, and painful, that is not always the case. Most have few or no symptoms, which can delay diagnosis and helpful antiviral medicines.

Having the virus can be a danger. Research has shown that anyone with HSV-1 or HSV-2 is twice as likely as noncarriers to later develop dementia. A pregnant woman with the virus can pass it to the infant during delivery, which can be fatal. And those who have HSV have much higher odds of HIV infection.

One thing is sure: With 25 million new cases of genital herpes a year, and the cost in health care and lost work time tagged at $35 billion a year, the need for prevention — and a cure — is urgent.