Can someone explain please?

[Lifestooshort1542]

I've heard that if you test for Covid symptoms after 5 days there's no point as it won't show up, but how can this be true if people who have tested positive at some point have been tested in hospitals further down the line and still been positive a month or two after? Kate far-away a husband for example kept testing positive for months until they finally got a negative Covid test.
Can someone explain please? :)
Thanks

In England you should test within 8 days of symptoms and in Scotland its 5 days. The tests can pick up fragments of virus even after you are no longer contagious so you can get a positive test if tested again within 90 days of the original test.