Herpes
Herpes can cause cold sores around the mouthReuters

Billions of people around the world have herpes, the highly infectious virus that causes cold sores around the mouth and genitals, the World Health Organization (WHO) has said. Globally, the herpes simplex virus type 1 (HSV-1) affects over 3.7bn people under the age of 50, while HSV-2 (which causes genital herpes) affects 417m people in the same age category.

HSV-1, which generally causes mouth ulcers, is usually caught in childhood, but the rate of contracting the virus during this time is reducing in rich countries due to improved hygiene and living standards. On the downside, young people are at an elevated risk of catching HSV-1 through oral sex when they become sexually active.

WHO medical officer Sami Gottlieb said: "HSV-1 has the potential to be transmitted from the oral area to the genital area through oral sex." With no cure available for either herpes virus, Gottlieb added: "We really need to accelerate the development of vaccines against herpes simplex virus, and if a vaccine designed to prevent HSV-2 infection also prevented HSV-1, it would have far reaching benefits."

Gottlieb noted that the figures are alarming given the discomfort caused by the infection and its potential to harm relationships and cause social stigma. She added that it has been demonstrated that HSV-2 infections increase the risk of HIV transmission.

"The new estimates highlight the crucial need for countries to improve data collection for both HSV types and sexually transmitted infections in general," said Dr Marleen Temmerman, director of WHO's Department of Reproductive Health and Research.

The report notes that 87% of Africans and 75% of those in the eastern Mediterranean and western Pacific regions who are under the age of 50 have HSV-1. Meanwhile, 39% of men and 49% of women in the Americas have the virus in contrast to 61% of men and 69% of women in Europe.