"Corona" refers to a very contagious (and very deadly, although mostly in older demographics) coronavirus, called COVID-19 or "the coronavirus" for short, that started around Wuhan in December 2019, spreading enough to be severely disruptive in China in January 2019 and turning into a full-blown pandemic by March 2020. A lot of things were locked down and quarantined because of it, in order to keep people safe, but this was delayed for so long that a lot of damage was already done by the time the measures where put in place. Now some places are apparently starting to open up again, even though we were warned more than a month ago that this short-term vigilance yet long-term abandonment would likely result in disaster. We can only hope that enough people will be able to continue to stay home to be safe without losing their homes and that the hospitals won't be overwhelmed (although please note that I do not advocate forcing people to do this, or anything else for that matter). There isn't a vaccine yet, so getting resistance to the virus is hard.