@Suasthuasanuas I'm sorry to hear about your son. I'm also sorry to say that we are still waiting for our ENT appointment to find out what is going on with his voice. We are seeing a paediatrician at the local hospital who doesn't have much to suggest or offer him, unfortunately.
I suspect the fatigue is Long Covid related, and we are following advice given on help groups and websites to pace himself etc. It's difficult to know what advice to take, and I long for better guidance and direction from the medical professionals. He is starting to show a bit more stamina than he had before, and he is back at school on reduced hours. Everything I've read indicates that children recover well with time and rest. That keeps me going.
We've sought out some alternative therapies for him. We also looked at potential allergies and had someone with some medical knowledge, time (and an open mind!), look at all his blood results. His iron was in 'normal range' but apparently very low for a boy of his age. We started iron supplements, which is making a positive difference.
With your son, at 13, there is also the effect of hormones and puberty to consider? They use so much energy up just growing, this must impact their recovery from a covid type virus? It's a long shot but have you tested for Lyme’s disease? It's a disease carried by infected ticks and it can result in symptoms similar to long covid. It can be treated with antibiotics. I wish you all the best and hope that your son recovers soon.
@Vik71 your post makes a lot of sense and resonates with my experiences so far. Thank you for the advice to check out Long Covid Kids.