Several vaccines and microbicides are being studied as potential cures.

More than half the world's population carries the herpes simplex virus commonly known as oral herpes, a new report from the World Health Organization found.

The study, published Wednesday in the journal PLOS ONE, reports that 3.7 billion people under age 50 carry the type 1 (HSV-1) virus, which is is primarily transmitted through mouth-to-mouth contact and usually manifests as cold sores. That amounts to two-thirds of the world's population in that age group.

Herpes simplex virus type 2 (HSV-2) is nearly always transmitted through skin-to-skin contact and commonly causes genital herpes. WHO notes that the new estimates show that HSV-1 also is a notable cause of genital herpes when transmitted through oral sex.

“Access to education and information on both types of herpes and sexually transmitted infections is critical to protect young people’s health before they become sexually active,” Dr. Marleen Temmerman, director of WHO’s Department of Reproductive Health and Research, said in a statement. “The new estimates highlight the crucial need for countries to improve data collection for both HSV types and sexually transmitted infections in general.”

The study broke down HSV-1 by region, showing the most infections in Africa:

Estimates for HSV-1 prevalence by region among people aged 0-49 in 2012

  • Americas: 178 million women (49%), 142 million men (39%)
  • Africa: 350 million women (87%), 355 million men (87%)
  • Eastern Mediterranean: 188 million women (75%), 202 million men (75%)
  • Europe: 207 million women (69%), 187 million men (61%)
  • South-East Asia: 432 million women (59%), 458 million men (58%)
  • Western Pacific: 488 million women (74%), 521 million men (73%)

Estimates of new HSV-1 infections among people aged 0-49 in 2012

  • Americas: 6 million women, 5 million men
  • Africa: 17 million women, 18 million men
  • Eastern Mediterranean: 6 million women, 7 million men
  • Europe: 5 million women, 5 million menSouth-East Asia: 13 million women, 14 million men
  • South-East Asia: 13 million women, 14 million men
  • Western Pacific: 11 million women, 12 million men

Neither type of herpes is fatal, except in very rare circumstances, but they can be damaging to mental well-being, relationships and physical comfort. WHO says it's determined to find relief for those who have the viruses.

"Given the lack of a permanent and curative treatment for both HSV-1 and HSV-2, WHO and partners are working to accelerate development of HSV vaccines and topical microbicides, which will have a crucial role in preventing these infections in the future," the report says. "Several candidate vaccines and microbicides are currently being studied."

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