What is the most common cause of acute sinusitis?

Acute sinusitis is primarily caused by viral infections, particularly following a viral upper respiratory tract infection. This viral infection leads to inflammation and swelling of the nasal passages, often resulting in blockage of the sinus openings. When the sinuses become obstructed, mucus can accumulate, creating an environment where bacteria may proliferate; however, the initial trigger is usually a virus.

The most frequently encountered viruses responsible for acute sinusitis include rhinoviruses and coronaviruses. While bacterial sinusitis can occur after the viral infection, it is less common as a direct cause in the initial presentation. The differentiation of acute sinusitis caused by viruses versus bacteria is crucial, as it influences treatment strategies; viral sinusitis typically resolves on its own, while bacterial infections may require antibiotic therapy.

Other factors, such as allergic reactions and fungal infections, contribute to sinus-related symptoms but do not represent the most common cause of acute sinusitis. Allergic reactions can lead to sinus issue exacerbations, but they do not directly cause the condition. Fungal infections usually occur in immunocompromised patients or in specific scenarios, making them rare in the context of acute sinusitis. Thus, when considering the broader patient population, viral infections are recognized as the leading cause of acute sinus