Breathing difficulties is not a typical symptom of flu, but a characteristic for some of its complications. It may be present as a mild discomfort, but heavy breathing, chest tension, and wheezing are never signs of flu! If you are experiencing these symptoms, a medical examination is needed.
Patients with chronic bronchitis or smokers will experience an episode of bronchitis during influenza infection. The flu can trigger asthma attacks and worsen the symptoms of it (only in patients who already suffer asthma).
In general, patients with chronic pulmonary diseases are prone to developing flu complications, and they should be particularly cautious about breathing difficulties during influenza infection.