Chilly weather and common respiratory infections often go hand in hand. Now, a new study details a previously unknown way that the immune system attacks viral intruders inside the nose—and finds it works better when it's warm. The starting point was previous research which found that nasal cells released "extracellular vesicles" (EVs)—a spray of tiny sacs that swarmed and destroyed bacteria upon inhalation. "The best analogy that we have is a hornet's nest," said Amiji. Like hornets defending a nest from attack, EVs swarm, bind to, and kill invaders. For the new research, the team set out to answer two...