According to a news release from the University of Wisconsin-Madison, a study of the full genetic code of herpes simplex virus type 1 confirms the “out-of-Africa” pattern of human migration.

Senior author Curtis Brandt, a professor of microbiology and ophthalmology at the University of Wisconsin-Madison, notes that HSV-1 typically causes cold sores around the mouth.

Brandt and his colleagues, Aaron Kolb and Cécile Ané, examined in contrast 31 strains of HSV-1 obtained in North America, Europe, Africa and Asia. According to Brandt, they were stunned by the result.

“The viral strains sort exactly as you would predict based on sequencing of human genomes. We found that all of the African isolates cluster together, all the virus from the Far East, Korea, Japan, China clustered together, all the viruses in Europe and America, with one exception, clustered together,” he notes.

“What we found follows exactly what the anthropologists have told us, and the molecular geneticists who have analyzed the human genome have told us, about where humans originated and how they spread across the planet.”

Geneticists investigate how organisms are connected by examining alterations in the sequence of “letters” on their genes. From an understanding of how rapidly a particular genome alters, they can construct a “family tree” that reveals when particular variants had their last common ancestor.

Research on human genomes has revealed that our ancestors came out of Africa approximately 150,000 to 200,000 years ago, and then expanded eastward toward Asia, and westward toward Europe.

Researchers have previously examined HSV-1 by studying a single gene, or a tiny group of genes, but Brandt says that this method can be deceptive.

“Scientists have come to realize that the relationships you get back from a single gene, or a small set of genes, are not very accurate,” he posits.

For this study, the researchers utilized high-capacity genetic sequencing and complex bioinformatics to examine the gigantic quantity of data from the 31 genomes.

The method of simultaneously examining in contrast the entire genomes of related viruses could also be helpful in determining why certain strains of a virus are a lot more deadly than others.

“We’d like to understand why these few viruses are so dangerous, when the predominant course of herpes is so mild. We believe that a difference in the gene sequence is determining the outcome, and we are interested in sorting this out,” Brandt notes.

The researchers split the HSV-1 genome into 26 pieces, built family trees for each piece and then integrated each of the trees into one network tree of the whole genome. It was this arrangement that complemented existing studies of human migration.

According to the researchers, the new study could even identify some complexities of migration. Every HSV-1 sample from the U.S. except one paralleled the European strains, but one strain that was isolated in the Lone Star State appeared Asian. The sample either originated from someone who had journeyed from the Far East, or it originated from a native American whose ancestors had traversed the “land bridge” across the Bering Straight approximately 15,000 years ago.

“We found support for the land bridge hypothesis because the date of divergence from its most recent Asian ancestor was about 15,000 years ago,” Brandt notes. “The dates match, so we postulate that this was an Amerindian virus.”

HSV-1 was the perfect virus for the study for several reason, including the fact that it is able to develop lifelong latent infections.

Plus, HSV-1 is a lot simpler than the human genome, which limits the cost of sequencing, yet its genome is much bigger than another virus that also has been utilized for this type of study.

The biggest takeaway from the study “was clear support for the out-of-Africa hypothesis. Our results clearly support the anthropological data, and other genetic data, that explain how humans came from Africa into the Middle East and started to spread from there,” Brandt professes.

The study’s findings are described in greater detail in the journal PLOS ONE.

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