Not exactly... The spell (cure noxious), is a low level priest spell and all priests get it somewhere around level 4.
The lvl 54 raid mob is the end of the quest to rid each server of the plague event forever. So far, one or maybe two servers have mounted the raid and killed the boss mob thus ending the plague on that server.
Each case of the plague lasts for about an hour and a half if you do nothing about it, but left un-cured, it has no real effect on your character. You will continue to successfully swing your weapon and cast your spells despite the puke and shiver animations.
If you do take the cure, you will be imune to further re-infection for a period of about 45 minutes.
If you can't find a priest to cure you, any NPC alchemist can sell you a cure for about 58c.
If you don't want to keep getting re-infected, stay out of the towns and villages as much as you can. It tends to linger in the closed spaces... I get it almost every time I stand around in the bank!