Help-Virus relapse?

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From: Anita 
Email: reck@goldrush.com

My horse came down with the virus that is going around, was symptomatic for about ten days, was treated with SMZ for 7 days, was doing great. No fever, no cough and no nasal discharge. Day 15 started to relapse again with temp creeping up and has  choking spells with some  nasal discharge, though not necessarily related to putting his head down as in a guttural pouch problem,  Not as sick as before but definetely tired of it all, laying down more often.
Any one experiencing this?  Any leads would be appreciated.

                     Anita and "Sam"