study shows
https://nypost.com/2020/04/01/half-of-coronavirus-patients-in-iceland-are-symptom-free-study/
Unfortunately, that apparently doesn't mean for the duration of the illness:
"“What it means in my mind, is that because we are screening the general population, we are catching people early in the infection before they start showing symptoms,” said Kári Stefánsson, founder of biopharma company deCODE Genetics, one of the testing firms."