Hello Gardiner,

Thanks for posting,

Yes it is very possible to get infected or contaminated by a carrier of an upper respiratory tract infection especially if it is viral flu. This implies that your son must have gotten it from his girlfriend. Given the fact that his throat culture came out negative it is most likely a viral infection and not bacterial or fungal. If he is presenting with other symptoms of his mouth, it will be worthwhile to redo another throat swap to make sure that there is no super bacterial infection. It that is the case, then a course of antibiotics will be necessary. Your son will require in addition to the antiemetic (or the script for the nausea), antiinflammatory + analgesia for pain, fever and swelling.

Hope this helps

Hello!
Typically a throat culture only looks for strep throat caused by one kind of bacteria. However it is still possible to have a sore throat and have a negative culture.
With his symptoms and history of kissing, I would also be concerned about Mononucleosis or in short Mono which is viral infection that often presents with sore throat, fever, headache, fatigue, etc. There is a rapid test called the Mono spot that could be performed.
For sinus infections, typically he is going to have a purulent (yellow-greenish) nasal discharge and pain over his sinuses (located on cheeks and forehead). If this is the cause, he may have a sinus infection however it is unlikely that she gave him the sinus infection but more likely gave him a viral upper respiratory tract infection and his sinuses were not able to drain which can lead to an infection. Many sinus infections will resolve on their own in 7 days however if they persist or continue to worsen, then antibiotics are needed at that point.

Good luck and take care :)