Suggest Treatment For Sore Throat, Post Nasal Drip And Headache

I have a very sore throat and some post nasal drip, headache and just a general ill feeling, (groggyness). I would normally attribute it to a sinus infection. However, I am a little concerned because I stepped on untreated sewage water yesterday that was coming from an overflowed manhole. These symptoms started almost immediately after and wondered if I should be concerned. I haven t experienced sore throat with my sinus infections before.