What causes acute pharyngitis?
Acute pharyngitis is an inflammatory condition of the pharynx—specifically the mucosa and lymphoid tissue of the oropharynx—that develops rapidly, typically over hours to a few days. It is most commonly caused by viral infections, with rhinovirus, coronavirus, influenza virus, parainfluenza virus, adenovirus, and Epstein–Barr virus (EBV) being frequent etiologic agents. In adults, viruses account for approximately 70–90% of cases; in children, the proportion is similarly high, though slightly lower due to a relatively higher incidence of bacterial causes.
Bacterial infection is responsible for a minority of acute pharyngitis cases—roughly 5–30%, depending on age and clinical setting—with Streptococcus pyogenes (Group A β-hemolytic streptococcus, or GAS) being by far the most clinically significant bacterial pathogen. GAS pharyngitis is notable for its potential complications, including acute rheumatic fever and post-streptococcal glomerulonephritis, which underscore the importance of accurate diagnosis and appropriate antimicrobial treatment when indicated. Less common bacterial causes include Neisseria gonorrhoeae, Corynebacterium diphtheriae, Chlamydia pneumoniae, and Mycoplasma pneumoniae, particularly in atypical or persistent presentations.
Non-infectious triggers—such as allergic reactions, environmental irritants (e.g., tobacco smoke, air pollution, chemical fumes), gastroesophageal reflux disease (GERD), and vocal strain—can also produce symptoms mimicking acute pharyngitis. These must be considered in patients with recurrent or refractory symptoms, especially when infectious workup is negative.
Accurate diagnosis relies on clinical assessment—including symptom pattern, physical findings (e.g., tonsillar exudates, tender anterior cervical lymphadenopathy, absence of cough), and selective use of rapid antigen detection tests (RADT) or throat culture—rather than empiric antibiotic prescribing. Overuse of antibiotics not only contributes to antimicrobial resistance but also fails to benefit the majority of patients whose illness is viral in origin.