“If SARS had conformed to the perverse pattern of presymptomatic infectivity, its 2003 emergence wouldn’t be a case history in good luck and effective outbreak response. It would be a much darker story. The much darker story remains to be told, probably not about this virus but about another. When the Next Big One comes, we can guess, it will likely conform to the same perverse pattern, high infectivity preceding notable symptoms. That will help it to move through cities and airports like an angel of death.”