Since we have existed, we have been plagued by numerous diseases and issues caused by bacteria and viruses. We even face problems due to parasites. We now live in a time when we have eradicated many diseases and have many solutions from antibiotics to vaccines to deal with others. We also live in a time when our solutions are weakening against a growing number of diseases as the agents that cause then develop resistance against things like antibiotics.
As the climate change as well, we are faced with new diseases and those that have spread into new regions. To top it all off, we are facing epidemics like the HIV epidemics in places like Africa and the United States, though the situation in Africa is much more severe. Sexually transmitted diseases are also on the rise. So the question is where did these diseases come from? That is the question that Simon Underdown and his team hopes to answer for the herpes virus.
The Herpes Virus
The herpes virus can be categorized into two types. There is the herpes simplex virus type 1 (HSV-1) and the herpes simplex virus type 2 (HSV-2). HSV-1 is primarily contracted through oral to oral interaction that results in infection around the mouth area (cold sores). While not as prevalent, HSV-1 can also be transmitted via oral to genital contact resulting in genital herpes. HSV-2 is the sexually transmitted form of the virus that results in genital and anal herpes. There are currently about 3.7 billion people around the world has HSV-1 and about 417 million people, from 15-49 years of year, around the world has HSV-2. These very large numbers are made worse by the fact that there is no current cure for herpes in either form and the virus stays with the infected for their lifetime.
Oral and genital herpes caused by HSV-1 and HSV-2 are generally asymptomatic. When symptoms do arise, they are in the form of mild to painful blisters and ulcers at the site of infection. The herpes virus is most contagious when there are symptoms, but is also contagious even when there are no symptoms. HSV-1 is generally contracted during childhood and HSV-2 is gets its start around the sexually active. Since there are no cures for the virus, the only treatment is the use of antiviral drugs to lessen the symptoms. One of the important point to note is that if you are infected with a particular herpes type, you cannot be reinfected with that same type, but you can be infected by another type.
There are situations where either type of herpes can create additional problems. In rare cases, HSV can be transmitted from mother to fetus, resulting in neonatal herpes. This occurs in 10 out of every 100,000 births around the world and the results can be fatal or lead to neurological disabilities. Neonatal herpes occurs primarily when a woman contracts HSV during the late part of her pregnancy. HSV-2 can lead to higher chances of acquiring HIV, usually by three times as much compared to HIV infection rate of population without HSV. Also, having HSV-2 and HIV can lead to higher chance of spreading HIV to others. Since HIV results in a compromised immune system, the symptoms of HSV-2 are greater.
The Origin of HSV-2
It was originally thought that HSV-2 co-speciated with humans when our lineage diverged from the ancestors of bonobos and chimpanzees. A Recent analysis of HSV-2, HSV-1, and chimp herpesvirus 1 (ChHV-1) showed that HSV-2 was related closer to ChHV-1 than HSV-1 and that HSV-2 and ChHV-1 separated from each other about 1.4 to 3 million years ago. Simon Underdown and his team believed that HSV-2 might have jumped from chimps to another hominin before it jumped to humans. To test this theory, the researchers used a probability-based network analysis that combined data from virus genetics, current human genetics, ancient human and hominin fossils, and geographical data of the past.
The researchers found that Paranthropus boisei was the most likely culprit in the transmission of HSV-2. They could have contracted HSV-2 from chimps as they hunted and scavenged ancient chimps. Homo erectus, our ancestor, appeared about 2 million years ago and evidence suggests that P. boisei and H. erectus congregated around Lake Turkana, Kenya. H. erectus brought when them hunting and butchery. This behavior combined with the close proximity to P. boisei lead to the hunting and consumption of P. boisei by H. erectus, which was the probably moment of transmission as HSV-2 jumped to our ancestors and entered our species.
While their analysis shows strong support for this path, the other path that was supported by the data was transmission from ancient chimps to Homo habilis to P. boisei and finally to H. erectus. It is possible that H. habilis and P. boisei entered into violent confrontations with each other and HSV-2 could have passed to P. boisei via open wounds and injuries during those battles. The virus was not based from H. habilis to H. erectus because the ancient records do not show any geographic interaction between the two species as only P. boisei could have both the HSV-2 and the geographic interaction to pass it to our ancestors.
Given the limitation of fossils and DNA, due to degradation, as well as limited records of things happening 2 million years ago, the research is supportive of the transmission path but does not fully prove it. More time and data would be needed to improve the probability network to give even more accurate data. Besides that, this sort of methodology would be useful to track the ancient movements of other ancient diseases as they made their way to humans.
While more information is sought into the history of herpes, the next step is to find a cure for this currently incurable condition. There are currently vaccines in the works and if successful, they will be put into more invasive trails to ensure they are effective. In the meantime, it is important to practice safe sex and take other preventative measures to not get infected and not infect others.