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The measles virus began infecting humans 1,400 years earlier than previously thought. Thus concludes a new study whose results may help in the fight against other human pathogens.
Approximately in the6th century BC C., some1,400 years before than is currently estimated, themeasles virus split from a closely related one that was transmitted between livestock, according to a new study published in the journalScience. Experts suspect that it arose when therinderpest virus, now eradicated, spread from animals to human populations.
Measles has always been an important target for both health authorities and scientists, as it is one of themicrobial enemies oldest of mankind. Until now, the accepted consensus dates its appearance around the end of the9th century AD C., although the uncertainty about it was very great.
To better define its origin, the team led byAriane dux, from the Robert Koch Institute (Germany), reconstructed the genome of this virus usinglung samples collected from a measles case from1912. “We were able to rebuild most of the measles virus genome, generating the oldest genome inRNA virus that infects humans sequenced to date ”, explains SINC Düx.
The experts compared thesequencing data with a 1960 disease genome, 127 modern genomes, and genomes from rinderpest and another livestock virus called PPRV. Thus, they tracked the appearance of measles in humans between the years1,174 a. C. and 165 d. C., with an average estimate in the year528 a. C.
“We found that the measles and rinderpest virus lineages split around the 6th century BC. This date marks the earliest possible moment for the appearance of this pathology in humans ”, adds Düx.
Although this work is not connected to clinical research and will not impact its diagnosis or treatment, it does draw a new portrait of the evolutionary history of measles, showing that the pathogen emerged much earlier than was suspected and at a time that coincided with the emergence of large urban centers throughout Eurasia and South and East Asia.
"At that time human populations were growing and large cities were forming, a prerequisite for a disease like measles, which needs large populations to persist," he continues.
The evolution of human pathogens
The authors hope their research will inspire similar studies on other viruses. In a related perspective, also published inScience, Simon Ho and Sebastián Duchêne, from the Universities of Sydney and Merlburne (Australia), discuss how our understanding of the origins of human pathogens has advanced.
“Two key tools are the theory ofmolecular clock and the extraction of ancient DNA ”, points out to SINC Duchêne. "Technological advances in ancient DNA and statistical modeling of molecular processes allow us to estimate with great precision the time in which severalpandemics important in humanity ”.
In the case of measles, the results are consistent with previous studies that suggest a correlation between population growth, population density and the appearance of pandemics, such as theBlack Death caused by bacteriaYersinia pestis.
"As for theSARS-CoV-2, this virus could go several decades without being detected in bats. However, its appearance in humans occurred during the last weeks of November, a few weeks before the Chinese authorities alerted of the appearance of the virus inWuhan”Says Duchêne.
For experts, estimating the date of appearance of pandemics has implications in epidemiology and in the efficacy of vaccines. First, understanding when these pathogens appear helps determine the rate of transmission and make predictions of the proportion of the population that will be infected.
"The analysis of genomes ofCOVID-19 in some countries, such as Australia, they have established risk factors for transmission. Controlling these factors has facilitated the mitigation of the pandemic ”, he insists. Second, the effect ofmass vaccination it is associated with the genomic diversity of pathogens. For example,measles genomic diversity it has been reduced thanks to vaccination campaigns in recent decades.
But why are some vaccination campaigns more effective than others? Duchêne has it clear. Due to their molecular clock, viruses with fast molecular rates, such as influenza, require annual vaccination, while some with slower rates, such as influenza.yellow feverThey can be controlled with much less frequent vaccination.
A. Düx; L.V. Patron; J.F. Gogarten; A. Hilbig; K. Merkel; B. Prepoint; S. Santibanez; J. Schlotterbeck; M. Ulrich; A. Mankertz; F.H. Leendertz; S. Calvignac-Spencer; S. Lequime; B. Vrancken; P. Lemey; S. Boral; D. Horst; N. Widulin; T. Schnalke; B. Prepoint; B. Prepoint; M.A. Suchard; T. Schnalke; K. Harper.Science https://science.sciencemag.org/cgi/doi/10.1126/science.aba9411
S.Y.W. Ho; S. Duchêne. Dating the emergence of human pathogens.Science https://science.sciencemag.org/cgi/doi/10.1126/science.abc5746