Thanks for placing your query through HCM.
I can appreciate your concerns.
Your doctor appears to be correct in suspecting viral illness.
testing is unlikely to be helpful.
Instead, you should see a ENT specialist
to rule out chronic sinusitis
Regarding swimming lessons, you should follow ENT doctors advice.
Hope I have answered your query.
If you have any further questions I will be happy to help.
Wish her a good health.