Is it possible that the Delta variant has been confused with hay fever?
Oooh maybe.
https://nationalfile.com/top-experts-say-covid-19-delta-variant-symptoms-are-identical-to-hay-fever-common-cold/
The ones who haven't been vaccinated are safe to fly because they have less risk of blood clots. But it might be wise not to fly at the moment because if your pilot has been vaccinated, he or she might develop a blood clot and die while flying the plane.
Of course there is generally a co-pilot who could take over flying the plane but probably in order to keep their jab sorry, I mean job, the co-pilot will also have been vaccinated. Therefore there is a risk that both pilots could suffer serious health issues whilst flying your plane. So at the moment it might be best not to fly anyway.
Stay safe.