The largest virus ever discovered has been found in a water-cooling tower in Bradford, England. It was lurking inside single-celled organisms
called amoebae, but its discoverers believe that it may also be capable of infecting humans.
Although the new virus is a thousand times smaller than a pinhead, its girth of 400 nanometres makes it a mammoth in the microbial world. Most viruses
measure between 10 and 100 nanometres, and the newcomer is even bigger than some bacteria.
The Mimivirus particles (green) are seen inside the amoebae (red)