As COVID-19 swept across the U.S. early last year, the primary concern was for the dying. So far, the pandemic has cost at least 645,000 American lives. But there are others – as many as 12 million and counting – who took months and months to recover, or are still struggling. These "long-haulers" suffer from what's called Post-Acute Sequelae of SARS-CoV-2 infection, better known simply as long COVID. Over the next five days on USATODAY.com, we will share stories of families desperate to regain what they've lost and scientists doing everything they can to help.