Measles started to infect people already in the sixth century BC, not the ninth century BC, as previously thought. This is the conclusion reached by the team of researchers, analyzing the viral genome by the method of molecular clock. In an article published in Science, scientists suggest that the ancestor of measles jumped from cattle soon after the arrival of the big cities. It is in these communities first appeared the conditions necessary for continued transmission of the disease.
The majority of infections transmitted to humans from wild or domestic animals. For example, the ancestor of the measles virus is now considered to be destroyed by the plague pathogen of cattle: estimates made using the method of molecular clock, indicatesthat the disease is cows learned to infect humans at the end of the ninth century of our era. However, this Dating can be inaccurate because they are based on relatively young samples, the oldest of which dates back to 1954, and the remaining allocated after 1990. Attempts to detect earlier signs of a measles virus still left unsuccessful, primarily because of the instability of RNA that makes up its genome.
A team of researchers led by Sebastian Calvignac-Spencer (Sebastien Calvignac-Spencer) from the Robert Koch Institute was able to solve this problem. They carefully studied the collection of samples of the lungs, which were collected from the 1870s to 1930-ies and is now in the Berlin Museum of medical history. Among them the researchers were able to detect preserved in formalin light two year old patient, who died from measles in 1912. The drug contained well-preserved viral RNA. In addition, scientists have found two relatively old sample, dated 1960. They are stored in one of the laboratories of Prague.
Comparing the decrypted genomes samples, 1912, 1954 and 1960 with a more modern, the authors were able to compile a phylogenetic tree of measles virus. It turned out that mass vaccination has dramatically reduced the genetic diversity of the infection. For example, the evolutionary line, which included strains from Berlin and Prague samples, completely extinct.
In the next step the team has made a database 51 of the viral genome. In addition to Berlin, Prague, and several younger specimens of measles virus, it included information about the causative agents of rinderpest and small ruminant plague. Applying to the sample a method of molecular clock, the authors came to the conclusion that the measles virus differed from the virus of rinderpest around the sixth century BC. It’s 1400 years earlier than previously thought.
The first description of measles was made in the tenth century ad Persian scientist and physician Abu Bakr Muhammad ar-Razi. This date probably coincides with previous estimates, which took the appearance of the disease to the ninth century of our era. However, the lack of clear references in the written sources cannot be taken as evidence of the late appearance of measles. Maybe her for a long time, just not separated from other similar diseases.
The authors believe that measles was finally able to gain a foothold in the human population shortly after the population of individual cities reached 250-500 thousand inhabitants. This critical threshold, providing continuous transmission of the disease, were overcome in the second half of the first Millennium BC, which coincides with the new molecular Dating. Prior to this, the ancestor of the measles could infect people, but they died or recovered before it had time to transmit the virus to a sufficient number of congeners.
Despite the availability of an effective vaccine against measles, in recent years, scientists anxiously noted the rapid growth in the number of new cases of this disease. The reason is that, under pressure of propaganda of antitreponemal more and more parents refuse to vaccinate their children. The consequences of such decisions can be catastrophic.
Sergey Knee High