Early divergent strains of Yersinia pestis in Eurasia 5,000 years ago.

The bacteria Yersinia pestis is the etiological agent of plague and has caused human pandemics with millions of deaths in historic times. How and when it originated remains contentious. Here, we report the oldest direct evidence of Yersinia pestis identified by ancient DNA in human teeth from Asia and Europe dating from 2,800 to 5,000 years ago. By sequencing the genomes, we find that these ancient plague strains are basal to all known Yersinia pestis. We find the origins of the Yersinia pestis lineage to be at least two times older than previous estimates. We also identify a temporal sequence of genetic changes that lead to increased virulence and the emergence of the bubonic plague. Our results show that plague infection was endemic in the human populations of Eurasia at least 3,000 years before any historical recordings of pandemics.

[The history of the flea in art and literature]. / La storia della pulce nell'arte e nella letteratura.

The flea has been, indirectly, one of the protagonists in the history of man. As one of the two vectors of Yersinia pestis, the etiological agents of the Black Death, the flea (Xenopsylla cheopis) has contributed, over the centuries, to the death of millions of people in many countries. Galileo Galilei was the first to observe the flea with a microscope (1624), but the credit of depicting it with a stunning drawing goes to the Britisher Robert Hooke in 1665. A number of zoologists, including Antonie Van Leeuwenhoek and Diacinto Cestoni, well described and illustrated the life cycle of the flea in the XVII century. Some of these reports inspired scholars such as J. Swift and J. Donne for the composition of classic poems. Also, the flea, alone and with its hosts, has inspired a number of artists to create fine paintings; among them: G. M. Crespi, G. B. Piazzetta, G. de la Tour and others. Colorful sonnets on the flea in the Roman dialect were written by G. Belli and Trilussa. The flea also, as a theme, inspired musicians such as G. F. Ghedini and M. Mussorgsky, play writers such as Feydeau and moviemakers such as Charlie Chaplin. The flea is, indissolubly, connected with the history of Black Death. This disease in man is, in fact, caused--as demonstrated by Yersin and Simond--by the triad: bacterium (Yersinia pestis)/rat/flea (Xenopsylla cheopis). Over the centuries, Black Death has had a deep impact on both the visual arts and literature and, as a result, a very large number of paintings and other works of art have been produced to remember these tragic episodes. In the field of literature, Black Death has been skillfully described by writers such as Boccaccio, Manzoni and Camus. Finally, in recent years, following the discovery of the existence of a large market for the control of fleas in small animals, the interest in this minute insect has been resurrected and, parallel to that, the rebirth of the flea iconography, through electromicroscopy, has also taken place.