Description

• Inflammatory disease of the lungs due to a viral infection
• Most viral pneumonia result from exposure infection in the form of aerosolized secretions.
• Hematogenous and direct spread are also possible.

Geriatric Considerations
High rates of morbidity and mortality in the elderly

Pediatric Considerations

• Adenoviral infections in children are serious.
• More serious respiratory viral infections are almost always seen in infants and in immunocompromised patients.

Pregnancy Considerations

• Pregnant patients should avoid contact with anyone who has a viral infection.
• Influenza vaccination is recommended for all pregnant women during the influenza season.

Epidemiology

Incidence

• Predominant age: children <5 years
• Predominant sex: male = female

Prevalence

• Prevalence is variable with seasonal outbreaks, but the disease is more common during winter months.
• ~90% of all cases of childhood pneumonias have a viral cause.
• Between 4% and 39% of pneumonia diagnosed in adults have been attributed to viral causes.

Etiology and Pathophysiology

Overall: Influenza A and respiratory syncytial virus (RSV) are the leading causes followed by adenovirus and the parainfluenza viruses.

• Adults
  • Influenza A, B, and C
  • Influenza H1N1
  • Adenovirus
  • Parainfluenza
  • Coronavirus/severe acute respiratory syndrome (SARS)
• Children
  • Influenza A, B, and C
  • Influenza H1N1
  • Rhinovirus
  • Adenovirus
  • Parainfluenza
  • Rubeola (measles)
  • RSV (particularly for those born prematurely)
• Miscellaneous
  • Cytomegalovirus (CMV) (particularly in immunocompromised patients)
  • Varicella
  • Herpes simplex virus (HSV)
  • Enterovirus
  • Rubeola
  • Epstein-Barr virus
  • Hantavirus
  • Human metapneumovirus

Genetics
No known genetic pattern has been recognized.

Risk Factors

• Seasonal: epidemic upper respiratory illness
• Living in close quarters
• Recent upper respiratory infection
• Travel to endemic area
• Nonvaccinated person
• Age >65 years or <5 years
• Altered mental status (due to dysphagia)
• Cardiac disease
• Chronic pulmonary disease (e.g., COPD, emphysema)
• Immunocompromised (HIV, transplant recipient, medication induced)
• Cystic fibrosis
• Kartagener syndrome

General Prevention

• General hand-hygiene techniques are the first-line prevention in transmission of infectious particles.
• Prevention of influenza:
  • Influenza vaccination: Routine vaccination is recommended for ALL persons aged ≥6 months.
    • Children who are 6 months to 8 years of age and receiving seasonal vaccination for the first time OR received only 1 dose of the vaccine prior to July 2018 should receive 2 doses 4 weeks apart.
    • Children who are 6 months to 8 years of age who received 2 doses of the influenza vaccine should receive 1 dose of the seasonal influenza vaccine the following year.
    • See the Centers for Disease Control and Prevention guidelines (1)[A] regarding the use of live attenuated vaccine versus inactivated vaccine.
  • Chemoprophylaxis:
    • For those patients who are unable to receive influenza vaccine (e.g., severe allergy to vaccine) and are at very high risk or have severe immunocompromised, oseltamivir or zanamivir may be used following an exposure to a person with influenza.
    • For those who did not receive the vaccine and have been exposed to influenza, use of oseltamivir or zanamivir is recommended for up to 7 days following exposure.
    • Institutional settings: During an influenza outbreak among nursing home residents, use of antiviral medications for chemoprophylaxis is recommended for all nonill residents (regardless of whether they have received influenza vaccination) for a minimum of 2 weeks, continued for 1 week after the last known case is identified.
• Prevention of RSV:
  • Palivizumab may be given to children <12 to 24 months with certain risk factors. See American Academy of Pediatrics recommendation (2).

Commonly Associated Conditions

• Rate of mixed viral–bacterial coinfection is ~20% and can lead to more severe illness or hospitalization.
• Fungal infection and Pneumocystis jiroveci pneumonia in immunocompromised patients