The coronavirus has hopscotched from China to Europe to the United States. Now, South America finds itself the epicenter of the pandemic, with Brazil being especially hard hit. US President Donald Trump is suspending travel from Brazil to the United States. Meanwhile, in the United States, it’s Memorial Day, the official start of summer. Marco Werman speaks with Caroline Buckee, an epidemiologist at Harvard’s T.H. Chan School of Public Health, about the latest on what we know and what we still need to know in order to contain the virus.