Viral pneumonia is a subset of atypical pneumonias, referred to as pneumonitides. In the beginning, if the bacterial pathogen were not identified by Gram staining procedure and if the pneumonia did not respond to the antibiotic treatment, they were referred to as atypical. Scientists have now developed number of rapid tests to determine the viral etiologies. Their use in the emergency department (ED) is increasing, as it is feasible, hence will assume a significant importance in the development of antiviral agents.
The severity of viral pneumonia may vary from a mild illness to severe hypoxemia that could be life-threatening disease. The most recent viral illness called severe acute respiratory syndrome (SARS) is associated with high mortality and morbidity.
Viral pneumonia is mainly caused by invasion of different viruses and accounts for almost 50% of the total cases of pneumonia. Early symptoms of viral pneumonia are almost similar to that of bacterial pneumonia. There could be increased breathlessness and worsening of the cough. Viral pneumonia will lower the immunity of the person and may make him susceptible to bacterial pneumonia. Viral pneumonia is generally milder than bacterial pneumonia as bacterial pneumonia tends to occur suddenly and cause high fever, often over 104oF, or 40oC. In comparison to viral pneumonia, the chest x-ray of a bacterial pneumonia patient shows larger patches (infiltrates).
Depending on whether the pneumonia the viruses cause is a primary manifestation or part of a multisystem syndrome of disease, categorization is made. Viruses that are primary manifestations of disease include influenza virus types A and B, RSV, adenovirus, parainfluenza virus, rhinovirus, Hantavirus, and cytomegalovirus (CMV). The viruses that cause pneumonia as part of a multisystem syndrome include varicella-zoster virus, Epstein-Barr virus, Paramyxovirus species (measles), CMV, and herpes simplex virus.
Community-acquired pneumonia is mainly caused by S. pneumoniae, and with the increase in the use of pneumococcal vaccines, the fact may change in the near future. However, viral pathogens can be the etiology of community-acquired pneumonia. In 40-60% of patients with community-acquired pneumonia, the etiologic agent has not been identified. Furthermore, lack of convincing associations between individual symptoms, physical findings, laboratory test results, and specific etiologies has made it difficult to accurately determine the etiology of pneumonia during the initial visit to the emergency department (ED). Chest radiograph is recommended in patients with suspected pneumonia so that complications such as pleural effusions can be detected. This also discourages the use of antibiotics in healthy patients with bronchitis and not pneumonia.
The respiratory syncytial virus is the most common agent to cause respiratory diseases in children. It is often accompanied by a skin rash and may not be distinguishable from acute bacterial bronchitis or bronchiolitis. It does not respond to antibiotics. Adenovirus is mainly responsible for producing viral pneumonia in children and young adults. It affects the upper respiratory tract and causes prominent rhinitis. Sometimes, it may develop into lower respiratory tract disease that includes bronchiolitis and pneumonia. Influenza A virus is causative agent of viral pneumonia in adults. This disease usually occurs during epidemics of influenza A – Asian ‘flu – but is very rare. The symptoms develop rapidly with progressive dyspnoea. Death may occur within hours if the patient is suffering from acute haemorrhagic disease of the lungs. However, pneumonia during influenza epidemics is the secondary bacterial infection, staphylococcus aureus or streptococcus pneumoniae being the causative agents.
Viral pneumonia is usually mild and the patient recovers without treatment. However, there are severe cases that require hospitalization. People who have impaired immune systems are more prone to viral pneumonia. Young children, people with HIV, patients with organ transplants, the elderly, and people under medications to suppress their immune systems in the treatment of autoimmune disorders are the ones susceptible to viral pneumonia.
Antibiotics are effective in treating bacterial and not viral pneumonia. Severe cases can be treated with antiviral medications. Supportive treatment like humidified air, increased fluids, and oxygen can be used in viral pneumonia patient. If the infection is serious, hospitalization may be necessary to prevent dehydration and to ensure proper breathing.
Viral pneumonia can be caused either by the influenza virus, respiratory syncytial virus (RSV), and the herpes or varicella virus. It could also be caused by the virus that brings on the common cold (parainfluenza and adenoviruses).
Symptoms of pneumonia caused by a virus usually takes a lot of time to develop and hence it may take several days or even a few weeks for you to call the doctor for help. However, this is not the case in bacterial pneumonia. The symptoms show up quickly and the patient becomes sick and therefore sees the doctor within a few days.
Viral pneumonia diagnosis is determined by finding traces of bacteria and a dominance of monocytes on sputum smears and by the absence of a likely bacterial pathogen. Identification of the virus is usually not as easy but is important during community outbreaks, among very ill patients and for those infected with treatable viruses. Exanthematous viral infections (eg measles, varicella or herpes) that have been complicated by pneumonia could be diagnosed on the basis of other connected clinical observations including the rash. A proper diagnosis of most respiratory infections requires samples of the virus from throat washings or tissue, biopsy specimens or serologic assays and from identification of typical inclusions in cytopathology. Most hospitals do not provide facilities for viral culture. The diagnosis of influenza is determined by the presence of typical symptoms during an outbreak of the disease and fluorescent antibody stain of respiratory secretions or serologic assays of acute and convalescent sera.
Your temperature, heart rate and blood pressure will be checked by the doctor. A small clamp, similar to a clothes pin would be put on your finger to verify your blood oxygen level. The doctor may listen to your heart and lungs to ascertain the cause of your symptoms and the severity of the ailment. If pneumonia is suspected, a chest x-ray will be recommended. Excluding special cases, blood tests are usually not helpful in diagnosis of pneumonia.
For lung infections resulting from herpes simplex, herpes zoster, or varicella (chickenpox) Acyclovir 5 to 10mg/kg q 8 hr for adults and 250 to 500mg/m2BSA q 8 h for children is advocated. Immune globulin (IV immune globulin or CMV immune globulin) and ganciclovir 5 mg/kg IV bid may be advised to treat CMV pneumonia in organ transplant recipients. But for patients with AIDS, this therapy has little documented benefit.
Certain influenza patients develop superimposed bacterial infections that may need to be treated with antibiotics. Streptococcus pneumoniae and Staphylococcus aureus are the main pathogens encountered in this condition. The rarer pathogens which could also infect influenza patients include Neisseria meningitides and Haemophilus influenzae, group A -hemolytic streptococci.
The prognosis largely depends on the patient’s age, the causative organism and associated diseases. The course of treatment is determined after identification of the pathogen.