Is viral sinus infection contagious before symptoms show up initially or is it contagious only after symptoms come out?

Both, for the virus.: The virus is contagious just before the symptoms appear, and during the first part of the symptomatic illness. There is no way to predict in an individual person when he will no longer be contagious (many people ask about this, but one can only guess when he will no longer be spewing viruses). However, the sinusitis may not be contagious, meaning not all who catch the virus actually get sinusitis.