> Usually, the viruses that humans care about are successful because they shut down both of these signalling programs. The coronavirus is different. “It seems to block only one of those two arms,” tenOever told me. It inhibits the interferon response but does nothing about the cytokines; it evades the local defenses but allows the cells it infects to call for reinforcements. White blood cells are powerful weapons: they arrive on an inflammatory tide, destroying cells on every side, clogging up passages with the wreckage. They are meant to be used selectively, on invaders that have been contained in a small area. With the coronavirus, they are deployed too widely—a carpet bombing, rather than a surgical strike. As they do their work, inflammation distends the lungs, and debris fills them like a fog.