Infectious Lung Disorder Viral Respiratory Tract Infection A respiratory tract infection caused by a virus. Viruses represent the most common causes of upper and lower respiratory tract infections and include rhinoviruses, influenza viruses, parainfluenza viruses, and respiratory syncytial virus. Viral Respiratory Tract Infection Disease or Syndrome Viral_Respiratory_Tract_Infection C27219 Viral Respiratory Tract Infection C0877203 Viral Infection