The virus on its way to Germany

The viral puzzle begins

It is no coincidence that at the end of the 19th century attention was focussed on the causes of tobacco plant diseases. Following a devastating tobacco disease, the German bacteriologist Adolf Mayer tried to establish a standard for the pattern of the disease in Holland. In 1886 he described its typical pathological chequered leaf pattern, which led him to coin the term tobacco mosaic disease, and postulated a bacterium as the cause of the disease.

Then Dimitri Iosifovich Ivanovski (1892) and Mayer's colleague Martinus Willem Beijerinck (1898) independently observed that the pressed juice of infected plants remained infectious even when passed through established bacteria filters. Whereas Ivanovski thought that a very small bacterium was the cause of the disease, Beijerinck was the first to speak of a virus (for the modern definition of a virus see chapter 4). Yet he was a long way from clarifying exactly what criteria distinguished it from a bacterium. He believed that finer filters would provide an answer; the results of diffusion experiments also suggested, to his mind, that a dissolved substance was involved.