Which virus is the most common cause of acute pharyngitis and tonsillitis?

Adenovirus is indeed the most common viral cause of acute pharyngitis and tonsillitis. This virus is responsible for a significant number of respiratory illnesses, particularly in children, and can lead to symptoms such as sore throat, fever, and swollen lymph nodes. Adenovirus infections are particularly prevalent in the late summer and early fall, aligning with the peak seasons for respiratory illnesses in general.

Streptococcus pyogenes, while a frequent bacterial cause of pharyngitis, especially in cases presenting with significant throat pain and fever, is less common than adenovirus in the overall population for acute viral cases. Rhinovirus and Herpes Simplex Virus are also associated with upper respiratory infections, but they are not typically the predominant causes of acute pharyngitis and tonsillitis as adenovirus is. Thus, the distinction lies clearly in the prevalence of adenovirus as a primary viral pathogen in these conditions.