On viruses

Did you know… 

Viruses … are the most abundant life form on Earth – there are more viruses in the world than all other forms of life added together. (They) ‘have invaded every niche occupied by living things, including the most inhospitable places like hydrothermal vents, under the polar ice caps, and in salt marshes and acid lakes’, writes Dorothy Crawford, Professor of Microbiology at the University of Edinburgh. 

We are taught to think of cells as small; the average human body, for example, is composed of 37 trillion of them. This helps put bacteria in perspective. Each bacterium is a single-celled organism. Ten thousand of them would comfortably fit on a grain of sand. But viruses make bacteria look like giants. The volume of a virus is around a million times smaller than that of a bacterium. So tiny are these most enigmatic of microbes that they remained invisible to the human eye until the invention of the electron microscope in the 1930s.