Respiratory viruses are said to be older than modern humans

The oldest known human virus has just been discovered in samples dating back 31,000 years. But this adenovirus, which still infects most young children today, would have been transmitted to us by our Neanderthal ancestors.

The virus breathing spoils our winters for at least 31,000 years. But their origin could even go back much, much further, even before the appearance ofhomo sapiens, suggests a new study by Danish and British researchers pre-published on the site bioRxiv.

Sofie Holtsmark Nielsen and her colleagues analyzed two teeth from human remains found at the Yana archaeological site in the far north of Siberia and dated 31,600 years ago. Previous DNA analyzes were able to determine that they belonged to children aged 10 to 12 years. By conducting more advanced analyzes, the team discovered the DNA traces of four herpesviruses, including herpes, in the teeth. simplex, responsible in particular for cold sores. But the teeth also contained DNA fromadenovirus Human C (HAdV-C), well known to cause mild respiratory conditions in children.

Oldest human virus: a record pushed back by 25,000 years

« This virus is the oldest in humans to date », assure Sofie Holtsmark Nielsen. The record so far belonged to a virusHepatitis B 7,000 years old (Read below). ” This therefore postpones direct evidence of human viral infections by 25,000 years. », Emphasizes the researcher. But the team didn’t stop there. She carried out a reconstruction phylogenetic virus, comparing ancient viral DNA to that of modern strains. Their common ancestor could thus be determined and dated. ” These viruses evolve with their cash respective hosts, sometimes over millions of years », Explains Sofie Holtsmark Nielsen. According to his conclusions, the oldest ancestor of adenovirus C would have appeared 701,850 years ago (with a range between 487,000 and 963,000 years), i.e. well before homo sapiens (35,000 years ago). Respiratory infections have therefore already affected our Neanderthal cousins ​​who roamed the savannah 300,000 years ago.

Viruses as old as life itself

« Our results suggest that diversity genetic current HAdV-C predates modern human origins and probably originates from our hominid ancestors, write the authors in their study. It is not known, however, whether this diversity is the result of divergent viral lineages migrating out of Africa with their human hosts, or of inter-species transmission from archaic humans outside of Africa. “. It is also impossible to know if these old viruses were more or less pathogens than today.

Thanks to advances in DNA analysis, researchers are now able to reconstruct the genomes virus from very incomplete genome fragments. Recent studies have thus made it possible to demonstrate that the measles virus emerged over 2,500 years ago, and that of the plague dates back 5,700 years. But viruses are arguably as old as life itself. Viruses were already infecting insects 300 million years ago, showed a 2001 study published in the journal PNAS.

Hepatitis B: the oldest virus ever sequenced

Article by Celine Deluzarche published on 05/17/2018

Two teams of researchers have sequenced the genome of an ancient hepatitis B virus from human teeth and bones. This virus, which would have circulated about 7,000 years ago, is significantly different from the one we currently know in humans.

Two recent studies have successfully identified and sequenced the genome ofold viruses of hepatitis B. The first, posted on May 10, 2018 on the bioRxiv site (where researchers share unpublished versions of their work), comes from a team led by Ben Krause-Kyora and Johannes Krause. These two German researchers analyzed three skeletal teeth dating from 1,000 to 5,000 BC. The second, whose main author is the zoologist Eske Willerslev (University of Copenhagen), has been published in Nature on May 9th. She looked at samples between 800 and 4,500 years old.

To reconstruct the genomes of viruses, Eske Willerslev and his colleagues have a little “Searched the trash”, jokes the researcher. They analyzed the sequences which had been eliminated because they did not belong to the human genome. It is from these pieces that we can reconstruct the genomes of viruses, “A bit like a puzzle”, summarizes Eske Willerslev, quoted by The Atlantic. In fact, it’s not a genome but multiple different forms of the hepatitis B virus (16 in the first study, 12 in the second) that the researchers found.

Even more surprisingly, none of these forms corresponds to a strain currently known in humans. However, five of them seem to be similar to strains observed in Africa in the chimpanzee and the gorilla. According to Krause-Kyora’s calculations, the hepatitis B virus has circulated in western and central Europe for at least 7,000 BC. So far, the oldest virus ever studied came from a mummified child of the XVe century in the Naples area.

Predict the evolution of current viruses

This discovery is very important because it tells us about the possible evolution of current viruses. Until now, only recent strains have been sequenced. “It’s like trying to understand evolution by studying only living animals”, illustrates Terry Jones, interviewed by theEvening Standard, researcher at the University of Cambridge and co-author of the study published in Nature. However, some of the mutations discovered are likely to return, observes Eske Willerslev, the main author. By studying these ancient forms, for example by injecting them into mice, one could observe their effects and their virulence. Studying old viruses also helps us understand the migrations of prehistoric men.

Hepatitis B is currently one of the most common viruses in humans. There are more than 250 million chronic carriers, according to’WHO, and the disease is believed to be responsible for nearly 900,000 deaths each year. Hepatitis B infects the foie but the virus circulates in the blood and therefore ends up in bones and teeth. Moreover, if the researchers were specifically interested in this virus, it is because its genetic material is composed of DNA and not ofARN (like those of Ebola, measles or influenza for example), which therefore makes possible its sequencing with conventional methods.

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