What is the main cause of acute bronchitis?

The primary cause of acute bronchitis is viral infections. Acute bronchitis often follows a viral upper respiratory infection, such as a cold or the flu. Common viruses responsible for this condition include influenza, rhinovirus, and coronavirus.

In the case of acute bronchitis, the bronchial tubes become inflamed as a result of the viral infection, leading to symptoms like cough, mucus production, and difficulty breathing. While bacterial infections can occur, they are less common and typically do not initiate the condition in the first place.

Fungal infections and allergens are not the primary triggers for acute bronchitis. Fungal infections are more associated with specific populations or conditions (e.g., immunocompromised individuals), and allergens may exacerbate pre-existing conditions like asthma or allergic bronchitis but are not direct causes of acute bronchitis. Thus, the correct understanding of acute bronchitis emphasizes the viral nature of its causation.