Which characteristic best describes acute bronchitis?

Acute bronchitis is primarily characterized by a persistent cough that can be either dry or productive, often producing mucoid sputum. This cough is typically the most prominent symptom and can last for several weeks following the initial viral infection that causes the condition. The presence of mucoid sputum indicates that there is inflammation in the bronchial tubes, leading to increased production of mucus, which the body attempts to expel through coughing.

While other options include symptoms like fever and wheezing, these are not defining characteristics of acute bronchitis. Fever may be present in some cases, but it is not consistent, nor is wheezing a primary feature, as wheezing is more commonly associated with asthma or other forms of obstructive lung disease. Purulent sputum might suggest a bacterial infection, but acute bronchitis is usually viral, leading to more clear or mucoid sputum. A gradual onset and fatigue can occur, but they are also not specific to acute bronchitis and are more generalized symptoms that could apply to a variety of respiratory conditions. Thus, the defining feature of acute bronchitis is the paroxysms of coughing, often productive but can also be dry, highlighting the characteristic nature of inflammation in the airways.