There was a time not that long ago when it was easy to tell the difference between viruses and the rest of life. Most obviously, viruses were tiny and genetically simple. The influenza virus, for example, measures about 100 nanometers across, and has just 13 genes.
Those two standards, it’s now clear, belong in the trash. Over the past decade, scientists have discovered a vast menagerie of viruses that are far bigger, and which carry enormous arsenals of genes. French researchers are now reporting the discovery of the biggest virus yet. The pandoravirus, as they’ve dubbed it, is 1,000 times bigger than the flu virus by volume and has nearly 200 times as many genes — 2,556 all told.
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