Viral pneumonia is defined as a disease entity wherein there is the viral causation of oxygen and carbon dioxide gas exchange abnormalities at the level of the alveoli, secondary to viral-mediated and/or immune response-mediated inflammation. The traditional role of viral pneumonia was as a disease found predominantly in the very young, the elderly, and those exposed to influenza. In the past, the diagnosis of viral pneumonia was predicated on it being somewhat a diagnosis of exclusion. History, physical exam, chest radiography, and available lab work (until recently) lacked sensitivity and specificity. Once bacterial pneumonia has been excluded, then viral pneumonia diagnosis was entertained.
Traditionally, the treatment of viral pneumonia revolved around supportive care:
The concepts of diagnosis, prevalence, clinical role, and treatment of viral pneumonia are in flux for several reasons.
1. There is a growing population at increased risk of viral pneumonia:
2. The availability of sensitive, specific, real-time-result-available testing for viral entities:
3. The positive feedback loop that results from improved viral pneumonia testing modalities:
4. The availability of safe, tolerable, and somewhat specific antiviral therapies:
5. The increasing role of viral pathogens in pneumonia and the increased realization of the role of bacterial and viral co-infection necessitate a higher clinical index of suspicion and early identification of viral pulmonary pathogens. Counterbalance seeing this new clinical burden is the availability of the following:
As pneumonia can be considered somewhat a final common pathway of infection, especially for those who are immune-compromised, a great number of viruses can cause pneumonia. In general, these viruses can be divided into those containing DNA or RNA as their nucleic acid. As this is a bit of an artificial division, a more meaningful approach to etiology is to define by clinical syndromes produced and demographics affected.
Etiologies of Viral Influenza
Respiratory syncytial virus (RSV)
Influenza A, B and C viruses
Parainfluenza viruses type 1, 2, 3, and 4
ParechovirusesEpstein-Barr virus (EBV)
Human herpesvirus 6 and 7
Herpes simplex virus
Minimi virusCytomegalovirus (CMV)
Middle East Respiratory Syndrome (Coronavirus)
Severe Acute Respiratory Syndrome (Metapneumovirus)
A number of epidemiological cues can aid in the diagnosis of viral pneumonia, including the following:
Age - Viral pneumonia is most common in the very young and in the elderly. There is a steep decline in the incidence of viral pneumonia from adolescence through the fifth or sixth decade of life. Then an upsurge as age-related immunosuppression and age-related pathologies result in immunosuppression increase.
Pregnancy - Viral pneumonia continues to be quite concerning in pregnancy. Of particular concern is influenza-related pneumonia secondary to the ubiquitous nature of influenza from late fall to late spring; the last two major flu epidemics, 1918 and 1957, produced respective mortality rates of 50% and 10%. This increased mortality is a major factor in the CDC recommendation that all otherwise healthy women receive an inactivated influenza virus vaccine during the second and third trimesters of pregnancy. An additional, though less common, cause of viral pneumonia in pregnant women is varicella. Limited data reflects a very substantial mortality rate, and current recommendations are for treatment with varicella-zoster immune globulin within 96 hours of exposure to varicella in a non-immune gravid female.
Immune competence - Decreased immune competence can be a result of the following:
The aforementioned may result in increased susceptibility to viral pneumonia.
Comorbid circumstances - A number of comorbid circumstances can predispose patients to viral pneumonia including:
On a macroscopic level, viral pneumonia can occur through one of three mechanisms:
On a microscopic level, the general pattern of viral pneumonia pathogenesis is as follows. Note that individual viral species causing pneumonia will have some variation from this scheme.
There are no pathognomonic history cues for the diagnosis of viral pneumonia as opposed to bacterial pneumonia. However, cues are suggestive in the differential diagnosis of viral pneumonia:
There are no pathognomonic physical examination findings for the diagnosis of viral pneumonia as opposed to bacterial pneumonia. However, physical findings are suggestive in the differential diagnosis of viral pneumonia:
As noted above, both history and physical examination may provide few diagnostic cues as to the etiology of pneumonia (bacterial versus virus). With the existence of specific effective treatment modalities, diagnoses of and identification of viruses causing pneumonia is of increased importance. Fortunately, the diagnostic acuity of laboratory examination in combination with radiography and history and physical examination has progressed. Laboratory Examination CBC with differential - There are no absolute diagnostic findings as viral pneumonia may result in elevated, normal, or decreased WBC counts. However, viral etiology is less commonly associated with elevated WBC and "left shifts" of the differential than bacterial types of pneumonia. Chemistry panel - Useful for gauging the degree of dehydration, relative renal dysfunction, and dosing of renal excreted medications C-reactive protein - As a reactive phase reactant, the CRP level may be elevated with viral pneumonia, although this is not a specific or sensitive finding. ELISA - rapid antigen tests - ELISA tests allow real-time data for a number of viral pneumonia pathogens. Commonly available ELISA tests include the following:
A caveat is that many viruses may be detected via ELISA in the presence of other known bacterial pathogens, and in some cases, the detection of a viral pathogen does not always indicate active disease. Gene amplification - First and second-generation PCR testing exists and may allow viral pneumonia etiology diagnosis within clinically relevant timing. Clinically available tests using PCR methodology include the following:
Cytological evaluation - No single cytological evaluation of patient tissue cells is entirely diagnostic for viral pneumonia. However, the generalization can be made that DNA viruses typically produce intra-nuclear inclusions, and RNA viruses typically produce cytoplasmic inclusions. Viral culture - Although viral cultures are the gold standard for the final diagnosis of viral pneumonia, there are limitations such as the following:
Viral antigens serology - The great majority of the viral entities involved in viral pneumonia have serological markers that can be obtained in the tract. Diagnostic problems include positive serology obtained for people with chronic viral infections that are not a factor in the presence of pneumonia and the limited use in acute treatment and decision making of viral pneumonia. Chest x-ray - As there is a tremendous overlap in findings on chest x-ray with both bacterial pneumonia and viral pneumonia, no one finding or set of findings is pathognomonic.
Features that are suggestive of bacterial pneumonia include the following:
Features that are more suggestive of viral pneumonia include the following:
Chest CT scan - The advent of thin-section CT scan has revolutionized the radiographic diagnosis of viral pneumonia. It has been observed, particularly in cases of viral pneumonia-like clinical presentation and normal chest radiography, thin-section CT scan will be positive for parenchymal defects and aid in diagnosis.
The cornerstone of treatment of viral pneumonia consists of the following: Supportive Care
Management of Comorbid Illnesses Appropriate treatment of Coexisting Bacterial Types of Pneumonia
Most current evidence indicates the frequent existence of concomitant bacterial types of pneumonia. The prototypical example is the observation that the majority of mortality during the 1917-1918 influenza pandemic was secondary to bacterial pneumonia, superimposed on the initial influenza pneumonia.
Specific antiviral therapy for a number of viral pneumonia exists as does preventative or prophylactic therapies for those at high risk would have been exposed:
Respiratory syncytial virus (RSV)
Herpes simplex virus (HSV)
Varicella-zoster virus (VZ)
The differential diagnosis for viral pneumonia is broad and includes the following:
Multiple variables determine the prognosis of each case of viral pneumonia, such as the following:
Complications of viral pneumonia include the following:
Patient education and preventative medicine play a key role in the clinical management of viral pneumonia:
An interprofessional team of healthcare workers manages viral pneumonia. While physicians may treat the infection, the role of the nurse and pharmacist are vital for prevention. The patient should be urged to get the annual influenza vaccine, as this can lower the morbidity and mortality. Pharmacists review prescriptions for dose and interactions and educate patients about side effects and the importance of compliance. All patients should be urged to quit smoking and abstain from alcohol. Further, patients should be educated about hand and personal hygiene to prevent transmission of the virus to others. Patients who are immunocompromised should be educated about the symptoms of pneumonia and when to seek medical care. Finally, patients should be urged to lead a healthy lifestyle, eat healthily, and exercise regularly. Close communication between the interprofessional team is essential if one wants to improve outcomes.  (Level 5)
The outcomes in most healthy people with viral pneumonia are excellent. However, in individuals who are immunocompromised or at extremes of age, the prognosis is guarded. Several adenovirus serotypes are known to cause severe pneumonia leading to bronchiectasis and irreversible atelectasis. It is estimated that anywhere from 10%-40% of children may suffer some irreversible lung damage after adenovirus pneumonia. Viral pneumonia in a patient with an underlying disease can add morbidity and lead to marked hypoxia. Overall, most patients recover with supportive measures and have no residual sequelae. (Level 5)
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