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Viral pneumonia is a subset of the pneumonitides, which were at one time called atypical pneumonias. In the past, all pneumonias were labeled atypical if a bacterial pathogen could not be identified with Gram staining and if the pneumonia did not respond to antibiotics. A number of rapid tests to determine viral etiologies have now been developed. Their use in the emergency department (ED) is becoming feasible and will assume increasing importance because of the development of antiviral agents.
Viral pneumonia can vary from a mild illness to a life-threatening disease with severe hypoxemia. Severe acute respiratory syndrome (SARS) is the most recent viral illness to be associated with high mortality and morbidity.
Viral pneumonia is caused by various viruses and accounts for half of all cases of pneumonia. Early symptoms of viral pneumonia are the same as those of bacterial pneumonia, which may be followed by increasing breathlessness and a worsening of the cough. Viral pneumonias may make a person susceptible to bacterial pneumonia. Viral pneumonia is usually milder than bacterial pneumonia. Bacterial pneumonia tends to occur more suddenly and cause higher fevers (often over 104oF, or 40oC). Also, usually larger patches (infiltrates) are visible on the chest x-ray, when the lung is affected by bacterial pneumonia than by viral pneumonia.
Viruses are divided into categories depending on whether the pneumonia they cause is a primary manifestation or part of a multisystem syndrome of disease. Those that cause pneumonia as a primary manifestation of disease include influenza virus types A and B, RSV, adenovirus, parainfluenza virus, rhinovirus, Hantavirus, and cytomegalovirus (CMV). Those that cause pneumonia as part of a multisystem syndrome include Paramyxovirus species (measles), varicella-zoster virus, Epstein-Barr virus, CMV, and herpes simplex virus.
Viral pathogens can be the etiology of community-acquired pneumonia. Although the most common cause of community-acquired pneumonia remains S pneumoniae (a fact that may change with the increasing use of pneumococcal vaccines), in as many as 40-60% of patients with community-acquired pneumonia, the etiologic agent is not identified. Furthermore, convincing associations between individual symptoms, physical findings, laboratory test results, and specific etiologies are lacking. Therefore, no way of accurately determining the etiology of pneumonia during the initial visit to the ED exists. It is recommended that a chest radiograph be obtained in patients with suspected pneumonia, both to find complications such as pleural effusions and to discourage the use of antibiotics in healthy patients with bronchitis rather than pneumonia.
In children, the respiratory syncytial virus is the most common agent. It may be indistinguishable from acute bacterial bronchitis or bronchiolitis and is often accompanied by a skin rash. It is unresponsive to antibiotics. Adenovirus may produce viral pneumonia in children and young adults. It more commonly causes upper respiratory tract disease with prominent rhinitis but on occasion, may produce lower respiratory tract disease, including bronchiolitis and pneumonia. In adults the principle viral cause of pneumonia is influenza A virus. This usually occurs during epidemics of influenza A - Asian 'flu - but is very rare. The condition develops rapidly with progressive dyspnoea; acute haemorrhagic disease of the lungs may cause death within hours. However, the most common cause of pneumonia during influenza epidemics is secondary bacterial infection, usually with Staphylococcus aureus or Streptococcus pneumoniae.
Most cases of viral pneumonia are mild and get better without treatment, but some cases are more serious and require hospitalization. People at risk for more serious viral pneumonia typically have impaired immune systems such as people with HIV, transplant patients, young children (especially those with heart defects), the elderly, and people taking medications to suppress their immune systems in the treatment of autoimmune disorders.
Antibiotics are not effective in treating viral pneumonia. Some of the more serious forms can be treated with antiviral medications. Other supportive care for viral pneumonia includes use of humidified air, increased fluids, and oxygen.. Hospitalization may be necessary to prevent dehydration and to help with breathing if the infection is serious.
Viral Pneumonia Causes
Viral Pneumonia Symptoms
Viral Pneumonia Diagnosis and Treatment
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