I've been really frustrated by this for ages. The WHO lists a whole range of symptoms for covid. Everyone I know who has had it didn't start their illness with fever, cough, loss of taste and smell, they started with headaches, body aches, runny nose, sore throat, fatigue or upset stomachs and then went on to develop characteristic symptoms.
Ignoring these other symptoms means people are not isolating and so spreading the virus in the first days of their illness. And that's not even touching on how children may well not even develop any of the 3 acknowledged symptoms at any point.
Now there are more tests available, surely it's time to start testing when people become unwell with a wider range of symptoms. I'd think this would be more effective than blanket testing populations to pick up the few asymptomatic.