Assalam Aleykum,
I think there are good supporters of Imam around the World, but likely not all of them are avoided Covid19. Might be they infected by it anyway because they might commit some sins or they'll be protected from it just because they follow Imam Mahdi and his call?
I read in the Quran that even a prophet Jonah ( peace be upon him) was punished by Allah ( Surah As-Saffat, 37: 139 to 148 ):
"And lo! Jonah verily was of those sent (to warn) (37:139)
When he fled unto the laden ship, (37:140)
And then drew lots and was of those rejected; (37:141)
And the fish swallowed him while he was blameworthy; (37:142)
And had he not been one of those who glorify (Allah) (37:143)
He would have tarried in its belly till the day when they are raised; (37:144)"