Description

• Inflammatory disease of the lungs due to a viral infection
• Most viral pneumonia results from exposure of a susceptible nonimmune person to infection in the form of aerosolized secretions.

Geriatric Considerations
High rates of morbidity and mortality in the elderly

• The 2009 H1N1 influenza pandemic had higher rates of morbidity and mortality than seasonal influenza outbreaks in the pediatric population.
• Adenoviral infections in children are serious.
• More serious respiratory virus infections are almost always seen in infants and in immunocompromised patients.

• Pregnant patients should avoid contact with anyone who has a viral infection.
• The 2009 H1N1 influenza pandemic had higher rates of morbidity and mortality than seasonal influenza outbreaks in the pregnant population.
• Influenza vaccination is recommended for all pregnant women during the influenza season.

Epidemiology

• Predominant age: Children
• Predominant sex: Male = Female

• Prevalence is unknown and varies with seasonal outbreaks, but the disease is more common during winter months.
• ~90% of all cases of childhood pneumonias have a viral cause.
• In different published series, between 4% and 39% of pneumonia diagnosed in adults has been attributed to viral causes.

Risk Factors

• Immunocompromised state
• Living in close quarters
• Seasonal: Epidemic upper respiratory illness
• Elderly patients
• Altered mental status
• Pediatric patients, particularly those <5 years of age or those born prematurely
• Cardiac disease
• Chronic pulmonary disease (e.g., COPD, emphysema)
• Cystic fibrosis
• Recent upper respiratory infection
• Travel to endemic area (e.g., Southwest US, which has hantavirus)
• Nonvaccinated person
• Avian flu [influenza A (H1N1)] is currently not a risk for persons in the US, but it is a risk for those with poultry (chicken, duck, and turkey) contact in Asia, Europe, and the UK.

Genetics
No known genetic pattern has been recognized.

General Prevention

• General hand hygiene techniques are the first-line prevention in transmission of infectious particles.
• Influenza vaccination: Routine vaccination is now recommended for ALL persons aged ≥6 months. This represents an expansion of prior recommended populations (1):
  • Children who are 6 months to 8 years of age and receiving seasonal vaccination for the first time should receive 2 doses rather than 1.
  • Children who are 6 months to 8 years of age who received ≥1 doses of the 2010–2011 seasonal influenza vaccine should receive 1 dose of the 2011–2012 seasonal influenza vaccine (2).
  • The 2011–2012 influenza vaccine includes coverage for H1N1 (2).
  • See the CDC guidelines regarding the use of live, attenuated vaccine vs. inactivated vaccine.

• For those patients who are unable to receive influenza vaccine (e.g., with an egg allergy or other) and are at very high risk because of age, comorbid illness, or another risk factor, oseltamivir or zanamivir may be used for the duration of the season, with special recognition for potential viral resistance (1).
• For those who did not receive the vaccine and have been exposed to influenza, use of oseltamivir or zanamivir is recommended for 7 days following exposure (1).

Etiology

Overall: Influenza A and respiratory syncytial virus (RSV) are leading causes followed by adenovirus and the parainfluenza viruses (3):

• Adults:
  • Influenza A, B, and C
  • Influenza H1N1
  • Adenovirus
  • Parainfluenza
  • Coronavirus
• 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
  • Avian influenza A (H1N1) is currently not a risk for persons in the US, but it is a risk for those with poultry (chicken, duck, and turkey) contact in Asia, Europe, and the UK.
  • Coinfection with bacterial pathogens is common.

Commonly Associated Conditions

• Rate of mixed viral-bacterial coinfection is ~20%
• Fungal infection and Pneumocystis jiroveci pneumonia in immunocompromised patients