Sunlight will help
Updated: Apr 7, 2020
Disclaimer: This piece is about direct sunlight helping to disinfect surfaces. It is NOT about curing people who already have Covid-19.
We now know that SARS-CoV-2 can survive on many surfaces for days at a time. Some examples are cardboard (about a day), plastic (up to 3 days), and steel (also up to 3 days).
So, it's more important than ever to regularly disinfect common surfaces. But constantly soaking surfaces in chemical disinfectant is prohibitively expensive or otherwise not possible for many people. That's where sunlight comes in to lighten the viral load.
Ultraviolet light (or UV light) is generally bad for viruses, though some are more sensitive than others. And sunlight always contains UV light. This is true even if it's cloudy and seems kind of dark outside. There is still UV light coming through - your human eyes just can't see it.
So, open your windows during the day! Not just your blinds, but the actual windows themselves. Glass is a partial UV blocker and will block some of the UV spectrum.
If you open your window blinds and windows, this will help reduce persistent contamination on any non-biological surfaces exposed to the sunlight - surfaces like countertops, floors, tables, and so on.
Just to be clear, this will help reduce surface contamination. It will NOT singlehandedly eliminate surface contamination.
The UV dose from sunlight does not always kill viruses as quickly or completely as the specialized and extremely dangerous UV lamps used for sanitizing surfaces in biological research labs and other settings, including lamps used to combat SARS-CoV-2 contamination.
All that said, it is worth repeating: sunlight will help.
However, sunlight will not help cure or disinfect an infected person. If the virus is in your body, sunlight can't reach it. Don't try to sunbathe yourself into recovery. You will only give yourself sunburns and skin cancer on top of your coronavirus infection.
Sunlight will not cure Covid-19 infections, but someday medicine will. For those who wish to keep track of therapeutic development, this paper is the best summary I have found for current scientific research efforts into Covid-19 medicines and vaccines.