Herpes simplex virus infection, or commonly known as herpes, is caused by either type 1 (HSV-1) or type 2 (HSV-2) virus. The former gives way to oral herpes or the infection in or around the mouth and is mainly transmitted by oral contact. On the other hand, the HSV-2 or genital herpes is almost exclusively sexually transmitted. According to the World Health Organization, genital herpes is a global issue, affecting an estimated 417 million people worldwide in 2012. It is not yet known the exact origins of the herpes simplex virus until a recent study done by a team of Italian scientists.
Both HSV-1 and HSV-2 can cause very serious -- and even fatal -- diseases and to better understand the origins of these viruses, researchers are able to get a glimpse of the complex evolutionary history of these two viruses. According to researcher Diego Forni, the team analyzed the diversity of the two viruses and their relation to their geographical origin. They noticed that there are viruses that although coming from distinct continents, does not show any difference and this disproves the earlier hypothesis on ancient migration. However, Forni clarifies, that their data is clear that the two herpes simplex virus originated in Africa. "Therefore, we thought it was necessary to estimate when the viral strains circulating nowadays among humans left Africa." He said.
This study, which is a collaboration between the IRCCS Medea and the University of Milan and has been published in Molecular Biology and Evolution, also notes that just like other viruses in the Herpesviridiae family, the types 1 and 2 of herpes simplex virus are very similar to those that infect the great apes in Africa. It is also explained that these viruses evolved together with their hosts and infected humans.
Even in modern times, Africa remains to be the continent where the viruses are most prevalent. Because of this, scientists hypothesize that viral strains affecting humans left the continent in "very ancient times". Experts previously thought that the spread of these viruses coincided with the migration of the modern human species 60,000 years ago. According to co-author Manuela Sironi, the scientific community gains better knowledge about the speed at which viral species evolve through viruses found in archaeological sites. She says that with the help of technology, scientists can now use precise methods that allow dating of the origin and the dispersal of the viruses, "By applying these methods, we estimated that the circulating strains of herpes simplex virus type 1 migrated from Africa about 5000 years ago." Sironi narrated. However, the exit of the HSV-2 virus from Africa was more recent. According to the studies, HSV-2 links epidemiological data and a major historical event: the transatlantic slave trade where millions of Africans were transported to the Americas where it became the second home to the virus.
Herpes virus is not only the disease that was introduced by the slave trade. In studies prior to this, it was shown that yellow fever and the parasitic worm Schistosoma mansoni were spread in the same way. Unlike HSV-2, however, these diseases stayed in the tropical and subtropical areas of the world.