My title is provoked by the traditional view of viruses as non-living, passive particles — still the prevalent opinion. That is understandable. After all, one could conceive of a virus as a letter flung out and floating on the breeze: a tightly sealed envelope containing a message taking random flight until it lands upon a hapless reader. It only comes to “life’’ when opened up by its recipient.
This picture of a virus is wrong. I will use the tools of statistical physics to show that the influenza-A virus is a mobile, hard-wired computer with a mechanical logic of binding and cleaving that empowers its motion through the receptor-rich landscapes of airways. It’s not just animate — it encodes a gradient-search strategy onto its outer envelope and senses its way to its target cells. This leads to clear fitness advantages — for itself. In its own way, the influenza-A virion thinks with its 2D surface, bridging the fields of physical chemistry and computation.