It's still the early days of the coronavirus pandemic, but history, biology and the knowledge gained from our first nine months with COVID-19 point to how the pandemic might end. The big picture: Pandemics don't last forever. But when they end, it usually isn't because a virus disappears or is eliminated. Instead, they can settle into a population, becoming a constant background presence that occasionally flares up in local outbreaks. Many emerging viruses become part of the viral ecology. The four coronaviruses that cause the common cold are endemic, circulating in the population, and the influenza strains that cause seasonal flu predictably surge each year. The SARS outbreak in 2003 didn't go the same way due to biology and behavior: It was much less transmissible than the virus that causes COVID-19, countries contained it quickly, and it has pretty much disappeared. One virus, smallpox, was eradicated through widespread vaccination, and polio may be close, after dec