Streptococcal pharyngitis (Strep Throat)
Neisseria gonorrhoeae
Diphtheria (C. diptheriae)
Bacterial Tracheitis
Infectious mononucleosis (EBV)
Patients with peritonsillar abscess have a 20% incidence of mononucleosis 
Laryngitis
Acute Bronchitis
Rhinovirus
Coronavirus
Adenovirus
Herpesvirus
Influenza virus
Coxsackie virus
Herpangina
Hand-foot-and-mouth disease
HIV (Acute Retroviral Syndrome)
Patients with peritonsillar abscess have a 20% incidence of mononucleosis 
Herpangina
Hand-foot-and-mouth disease
Stevens-Johnson Syndrome
Pemphigus
Angioedema
Deep neck space infection
Retropharyngeal abscess
Ludwig's angina
Parapharyngeal space infection
Peritonsillar Abscess (PTA)
Epiglottitis
Kawasaki disease
Penetrating injury
Caustic ingestion
Lemierre's syndrome<unk> 
Lymphoma
Internal carotid artery aneurysm
Oral Thrush
Parotitis
Post-tonsillectomy hemorrhage
Vincent's angina
Acute necrotizing ulcerative gingivitis
Retropharyngeal abscess
Ludwig's angina
Parapharyngeal space infection
Peritonsillar cellulitis
Streptococcal pharyngitis 
Epiglottitis
Neisseria gonorrhoeae
Retropharyngeal abscess
Diphtheria 
Peritonsillar abscess
Bacterial Tracheitis