Is this a new infection?

[MrsJThornton]

DS tested positive for covid on 24th November. No symptoms other than headache and tired. Isolated for 10 days then back to school. Last week started feeling poorly and developed nasty cough yesterday. I know that LFT can show as positive for up to 90 days after infection but we are due to see elderly relatives at Christmas and am worried he's got it again and we won't know for sure? WWYD? Would a PCR be more reliable at telling if it's a "new" infection?

A PCR could still be positive for 90 days there is no way of knowing if it’s a new infection or not.
However if he is unwell it would be unwise to meet with anyone - you wouldn’t want to pass whatever he has to them anyway surely?

That’s what I thought, but we need to take the test in order to be able to travel on Thursday and he could be over this round of illness (whatever it is) by then so thought I would ask as guidance is unclear (states you do need to take a PCR if any new symptoms occur but that they are inconclusive within 90 days). Obviously we wouldn’t travel anyway if he was still ill with anything by Thursday afternoon. Thanks