They can lie low, quietly infiltrating the body’s defenses, or go on the attack, making many copies of themselves that explode out of hiding and fire in all directions. Viral attacks are almost always suicide missions, ripping apart the cell that the virus has been depending on. The attack can only succeed if enough other healthy cells are around for the the newly emerging viruses to infect. If the barrage of viral particles hits nothing, the virus cannot sustain itself. It doesn’t die, since viruses aren’t technically alive, but it ceases to function.

So for a virus, the key challenge is deciding when to flip from chill mode into kill mode. To read the full story.