Pulmonary Pathology of Respiratory Viral Infections: Influenza, RSV, and SARS-CoV-2

Pulmonary Pathology of Respiratory Viral Infections: Influenza, RSV, and SARS-CoV-2

Respiratory viruses commonly target the lungs. Influenza, respiratory syncytial virus (RSV), and SARS-CoV-2 cause significant pulmonary disease. Each virus produces distinct yet overlapping patterns of lung injury. Understanding these pathological changes helps explain clinical severity.

Influenza primarily infects the airway epithelium. The virus damages ciliated cells in the bronchi and bronchioles. This injury leads to epithelial necrosis and desquamation. Inflammatory cells then infiltrate the airways and surrounding tissues. In severe cases, the infection extends into the alveoli. Diffuse alveolar damage can develop. Hyaline membranes and oedema appear in the lung tissue. Secondary bacterial infection often complicates the picture.

RSV mainly affects young children and older adults.

The virus shows a strong preference for smaller airways. It causes inflammation and necrosis of bronchiolar epithelium. Mucus plugs frequently obstruct the airways. Lymphocytic infiltration surrounds the affected bronchioles. In more severe infections, the process spreads to the alveolar spaces. Interstitial inflammation and oedema then become evident.

SARS-CoV-2 produces a broader pattern of lung injury. The virus enters cells through the ACE2 receptor. It damages both airway and alveolar epithelial cells. Early stages show mild interstitial inflammation. As the disease progresses, diffuse alveolar damage becomes prominent. Hyaline membranes form along the alveolar walls. Vascular injury also appears frequently. Microthrombi develop in small pulmonary vessels. Organisation and fibrosis may follow in later stages.

These three viruses share some common pathological features. All can cause epithelial injury and inflammation. All may progress to diffuse alveolar damage in severe cases. However, their preferred sites of injury differ. Influenza often begins in larger airways. RSV targets bronchioles more selectively. SARS-CoV-2 involves both airways and the vascular compartment.

Host factors influence the final pathological picture.

Age, immune status, and pre-existing lung disease modify the response. Timely recognition of these patterns supports better clinical understanding. Continued study of lung pathology remains essential for improving outcomes in respiratory viral infections.