Half of those tested, or half of those who tested positive? There’s an enormous difference!!!!!
This piece is so poorly written that it’s impossible to tell. I think I’ll try to find the original source.
But, you could read this in several ways:
1) They did random testing of a statistically meaningful percentage of the population, and have extrapolated from that to show that 50% of the population is infected, or has had the disease (can’t tell which)
2) Or, the author doesn’t bother to say what percentage of the population is positive, but turns to the separate question of symptoms. IE, of that (undisclosed) percentage of the population that tested positive, 50% showed no symptoms at the time of the test.
I think it’s the latter, but it’s impossible to tell from the word salad this writer scribbled out for the Mail.