Oropharyngeal infections are commonly caused by viruses, and the frequent pathogens are identified in Table 7.1. In adults, viral infection accounts for 80-90% of pharyngitis, with this figure reducing to 60% in children.

It is difficult to differentiate clinically viral infections from bacterial infections of the oropharynx, but the latter are more likely to present with severe local and systemic symptoms such as high-grade fever. Viral infections are more likely to be associated with nasal blockage and discharge. Throat swab cultures will identify bacterial pathogens, but this should be interpreted in the clinical context, as bacterial contaminants are common. Anaerobes such as Bacteroides species may have a greater role to play in peritonsillar abscesses but can be cultured from infected tonsils. Most uncomplicated infections of the oropharynx need symptomatic treatment only, and antibiotics are indicated in less than 20% of patients.

In acute pharyngitis (7.1) clinical symptoms include sore throat, halitosis, odynophagia, and tender cervical lymph nodes. The adenoid and tonsil hypertrophy associated with
the infection can cause mouth breathing, snoring, or even sleep apnoea. Systemic symptoms such as low-grade fever, lethargy, and malaise are common. Examination will reveal an inflamed pharynx with exudate or mucopurulent discharge running down from the pharynx. The tonsils may show mild inflammation.

When tonsillitis is present, the predominant findings can include all of the above with spots of exudates, or perhaps even a membrane covering the whole of the tonsils (7.2). Palatal petechiae can be present in both bacterial (typically Group A streptococci) and viral infections (typically with Epstein-Barr virus). Systemic examination is largely unproductive in the majority in identifying the pathogen. Presence of mucocutaneous ulceration, in the anus and genitalia, occurs during the acute seroconversion illness in HIV infection. Sometimes, the tonsillar hypertrophy is asymmetrical during an infectious episode (7.3). Follow-up is needed to ensure that the asymmetry settles down. Persistent enlargement of one tonsil should be investigated further to exclude neoplasm, and commonly tonsillectomy and histological examination is recommended. Lingual tonsillitis is a rare presentation (7.4A, B).