Could a flu virus cause HA dermal filler injection sites to become tender and swell?

This is difficult to answer without pictures. I recommend following up with your injector. If necessary, the filler can be reversed with hyaluronidase. See an expert. Best, Dr. Emer

Yes, it is possible to develop inflammation around the filler after an infection.  Please return to your doctor who can give you medication to clear the infection.

Thank you for your question.  I am sorry you are experiencing this.  It would be useful to know what HA filler you were injected with.  Recently some of the fillers in the Juvederm family (in particular Juvederm Voluma) have been reported to cause delayed facial swelling that usually occurs after a mild infection or illness (usually upper respiratory tract infection).  In the reported cases the swelling has always subsided, but nonetheless I would discuss this with your physician injector or be evaluated by an experienced physician. Best of luck to you.