Pulmonary Disorders Chapter 73.
Many viruses can cause bronchitis, and a few cause pneumonia.
Most common among infants and children are respiratory syncytial virus, parainfluenza virus, and influenza A and B viruses. Among otherwise healthy adults, the only frequently recognized viral pathogens are influenza A and B viruses. Important pathogens among the elderly include influenza, parainfluenza, and respiratory syncytial viruses. With this exception, most viral infections result from exposure of a nonimmune person to infected persons who are shedding the implicated virus. Alveoli may contain fibrin, mononuclear cells, and occasionally some neutrophils.