DefinitionViral pneumonia is an inflammation (irritation and swelling) of the lungs caused by infection with a virus.See also:Atypical pneumoniaInfluenzaMycoplasma pneumoniaRespiratory syncytial virusAlternative NamesPneumonia - viralCauses, incidence, and risk factorsPneumonia is an infection of the lung that affects 1 out of 100 people annually. Viral pneumonia is caused by one of several viruses, including influenza, parainfluenza, adenovirus, rhinovirus, herpes simplex virus, respiratory syncytial virus, hantavirus, and cytomegalovirus.People at risk for more serious viral pneumonia typically have weakened immune systems. This includes young children, especially those with heart defects, and the elderly. The following also weaken the immune system and raise the risk for pneumonia:HIVMe