Discovery of Viruses

Viruses redefined the boundary between life and non-life. The 1892 discovery by Dmitri Ivanovsky and Martinus Beijerinck unveiled filterable agents 100–1,000 times smaller than bacteria, challenging fundamental definitions. Unlike the Krebs cycle (#8), which describes energy extraction in healthy cells, viruses hijack host machinery to replicate. This discovery explained diseases like polio and rabies, and today over 200 million viral infections (e.g., COVID-19, HIV) are diagnosed globally each year, underscoring its monumental public health impact.