I had the flue for 13 days felt better than 2 days after have phlegm in throat does it have to do with the flue i was sneezing before also is it normal to have phlegm after having the flue n how long wil it last?

What was originally a viral upper respiratory tract infection could have developed into a bacterial infection after 7-10 days. A sinus infection would then cause ongoing nasal or postnasal drainage of discolored mucus. A bronchitis would cause coughing up of discolored phelgm. If symptoms persist a course of an appropriate antibiotic may be needed.