Chris Mooney reports on the science of why some younger people are getting better, while others are dying of covid-19. Griff Witte reports on how parties and gatherings became clusters. And Annie Gowen on coronavirus deniers. Read more:The medical mystery of why some people under age 50 are dying of covid-19.The coronavirus had already reached the United States, but the parties went on. Experts say the inconsistent manner that social gatherings shut down across states gave the illness a head start.Some people deny the seriousness of the global pandemic as a plot to get President Trump.  Follow the Post’s live coronavirus coverage here. Subscribe to The Washington Post: https://postreports.com/offer