My workplace has not yet required people to work from home (although they're talking about instituting this on Monday). But I know from experience that I personally tend to be about 25% less productive when I work from home, because I don't have a suitable work space.
Quite a drop, actually. I'm away from all my equipment, my jury-rigged home office is suboptimal, and having family around that doesn't understand work boundaries is distracting.
Maybe with practice and investment, things would be better but having to do so suddenly like this, nope.
People are worried, constantly checking the news and distracted because of it. It doesn't matter where they're working from, productivity is going down.