Cover image

ON THE COVER:

Rat flea. Coloured scanning electron micrograph of the head and mouth parts of the rat flea, Xenopsylla cheopis. The rat flea plays a major role in the spread of Yersinia pestis, the bacterium that causes bubonic plague (the Black Death of the Middle Ages). The bacterium is carried by the rat flea, which in turn infests domestic and brown rats, which live closely with humans. Extensive control measures, directed against the rats and fleas, have essentially banished plague from Europe, but there are still many regions of the world where the disease occurs and, at intervals, breaks out in an epidemic. Magnification: x125 at 6x7cm size. x300 at 8x10 inch size.

Photo by Dr. Tony Brain. Licensed by Clinical Medicine & Research for reproduction from Photo Researchers, Inc. (www.sciencesource.com).

See related article: Current Trends in Plague Research: From Genomics to Virulence, pp. 189–199.

In this issue of Clinical Medicine & Research, Huang and colleagues describe the genetic research into bacteria in the Yersinia genus in an effort to explain the difference in virulence and pathogenicity seen between Yersinia pseudotuberculosis and Yersinia pestis, the etiological agent of plague. Such research has generated information that may be used in developing diagnostic tests and vaccines to combat plague.