Viral pneumonia is a lung infection caused by any of a large number of viral pathogens. Some of the most important viruses are discussed in this chapter.

Viral pneumonia

Nonbacterial pneumonia

• COVID-19: Wide range, from mild symptoms to severe illness
  1. Fever, chills, fatigue, myalgias, headache
  2. Cough, shortness of breath, sore throat, congestion, rhinorrhea
  3. Loss of taste or smell
  4. Nausea, vomiting, diarrhea
• Influenza:
  1. Fever, cough, or sore throat (referred to as influenza-like illness [ILI])
  2. Uncomfortable or lethargic appearance
  3. Prominent dry cough (rarely hemoptysis)
  4. Flushed skin and erythematous mucous membranes
  5. Rales or rhonchi
• RSV, parainfluenza, and human metapneumovirus:
  1. Fever
  2. Tachypnea
  3. Prolonged expiration
  4. Wheezes and rales
  5. Diarrhea²
• Adenoviruses:
  1. Hoarseness, pharyngitis
  2. Conjunctivitis
  3. Tachypnea
  4. Cervical adenitis
• Measles:
  1. Conjunctivitis
  2. Rhinorrhea
  3. Koplik spots (white lesions on the buccal mucosa)
  4. Exanthem (maculopapular rash that starts on the head, then moves down to rest of body)
  5. Pneumonitis (coincident with rash, may also develop after apparent recovery from measles)
  6. Fever
  7. Dry cough
• Varicella:
  1. Fever
  2. Maculopapular or vesicular rash (all lesions at the same stage) becomes encrusted
  3. Pneumonia typically 1 to 6 days after rash appears. Pneumonia (Fig. E1) may be accompanied by cough and occasionally hemoptysis
  4. Few auscultatory abnormalities noted on examination of the lungs
• CMV:
  1. Fever
  2. Paroxysmal cough
  3. Occasional hemoptysis
  4. Diffuse adenopathy when pneumonia occurs after transfusion
  5. Severe immunosuppression associated with symptomatic CMV pneumonia (may be reactivation of latent infection or in previously seronegative recipients from the donor)

Viral infection can lead to pneumonia in both immunocompetent and immunocompromised hosts.

• Bacterial pneumonia; primary bacterial, secondary bacterial infection, or bacterial coinfection
• Other causes of atypical pneumonia:
  1. Mycoplasma spp.
  2. Chlamydia spp.
  3. Coxiella spp.
  4. Legionnaires disease.
  5. In certain patient populations (e.g., immunocompromised) consider fungal infections, pneumocystis, tuberculosis, or atypical mycobacterium.
• Acute respiratory distress syndrome (ARDS)
• Pulmonary emboli

• Information about the current prevalent strain of influenza virus or local prevalence of COVID-19 can be obtained from local health departments or from the Centers for Disease Control and Prevention.
• Influenza and other viruses may be cultured from respiratory secretions during the initial few days of the illness (special media and techniques necessary).
• Respiratory viral panels that use PCR-based assays from nasopharyngeal or bronchoalveolar lavage samples to test for a variety of viruses are extremely sensitive and are becoming the test of choice.
• Rapid flu tests have a 50% to 70% sensitivity in diagnosing influenza (a negative test does not mean the patient does not have influenza).
• Measles and adenovirus pneumonia are usually diagnosed clinically and can be confirmed with serology.
• CMV may be grown in culture or PCR amplified from bronchoalveolar lavage samples.
• An algorithm for the workup and management of suspected severe influenza pneumonia in the critical care unit is described in Fig. 2.
• COVID-19 can be assessed by nasopharyngeal or tracheal aspirate PCR tests for diagnostic workup. Rapid antigen tests are also available and provide results more quickly; however, a single negative test does not rule out an infection, especially in those who are asymptomatic. Antibody serology testing is not generally useful for acute diagnosis.

• COVID-19, influenza, RSV, and several other respiratory viruses can be assessed by nasopharyngeal or tracheal aspirate PCR tests for diagnostic workup.
• Sputum Gram stain (usually produced in scanty amounts) typically shows few polymorphonuclear leukocytes and few bacteria.
• White blood cell count may vary from leukopenia to modest elevation, usually without a leftward shift. COVID-19 is particularly characterized by leukopenia with predominant lymphopenia.
• Disseminated intravascular coagulation occasionally complicates adenovirus type 7 pneumonia.
• Multinucleated giant cells on Tzanck preparation of an unroofed vesicular lesion are useful in diagnosing varicella (also found in herpes simplex).
• CMV PCR can detect CMV virus but may be negative even with organ involvement in immunosuppressed patients.
• Cultures (blood, sputum, or bronchoalveolar lavage) may be helpful in identifying superinfecting bacterial pathogens.

• Chest x-rays may demonstrate a spectrum of findings from ill-defined, patchy, or generalized interstitial opacities (Fig E1), which can be associated with ARDS.
• Chest CT most commonly demonstrates ground glass opacities, which are usually patchy and peripheral in COVID-19.
• A localized dense alveolar opacification suggests a superimposed bacterial pneumonia.
• Small, calcified nodules may develop as a radiographic residual of varicella pneumonia.

General:

• Measures to diminish person-to-person transmission.
• Maintenance of adequate hydration.
• Possible ventilation support for severe pneumonia or ARDS.

COVID-19:

• Facial coverings, social distancing, and quarantine are important in limiting spread of disease.
• COVID-19 vaccines became available in the United States in December 2020. The messenger RNA vaccines (Pfizer and Moderna) require two doses and a booster. The Janssen vaccine requires a single dose and can be given as a booster, but the CDC generally recommends Pfizer or Moderna for both primary series and booster.³ Vaccines have been proven to be effective in reducing severity of illness in COVID-19 pneumonia.

Influenza:

• Yearly prophylactic strain-specific influenza vaccination can be given to prevent infection.

RSV:

• Isolation techniques are important in limiting spread of RSV infections.
• Immunoglobulins with a high RSV-neutralizing antibody titer are beneficial in treatment.

Adenoviruses:

• Intestinal inoculation of respiratory adenoviruses has been used to successfully immunize military recruits.
• Although they produce no disease in recipients, the viruses may be shed chronically and may infect others at a later date.
• These vaccines are not available for civilian populations.

Varicella:

• Live, attenuated varicella vaccine has been successfully used in clinical trials.
• Varicella-zoster immune globulin should be administered within 4 days of exposure to prevent or modify the disease in susceptible persons.
• Nonimmunized persons exposed to varicella are potentially infectious between 10 and 21 days after exposure.

Measles:

• Effective measles vaccine (MMR) is available.
  1. The vaccine should be administered at age 15 mo.
  2. A second dose should be administered at the time of school entry.
• Live, attenuated vaccine or gammaglobulin can prevent measles in unvaccinated persons if administered early after exposure.
• Vitamin A given PO for 2 days reduces morbidity and mortality rates from measles in exposed children.

• General: Administer antibiotics for bacterial superinfections when appropriate.
• COVID-19:
  1. Supportive care is the mainstay of treatment in outpatient and inpatient cases.
  2. Remdesivir has been shown to shorten the time to recovery in adults hospitalized with COVID-19 with lower respiratory tract infection.
  3. Dexamethasone decreases 28-day mortality in patients requiring respiratory support.
  4. Paxlovid has been shown to reduce the risk of hospitalization and death when used in the outpatient setting in patients who are at high risk for progression to severe disease. Individuals considered at high risk include age >50 yr, unvaccinated status, and specific medical conditions (e.g., diabetes, immunocompromised individuals).⁴
  5. In situations when Paxlovid and remdesivir are not available or cannot be administered, bebtelovimab and molnupiravir can be used.⁴
• Influenza:
  1. Oseltamivir is recommended in patients of any age suspected or confirmed to have influenza.
  2. Oseltamivir is recommended in outpatients with complicated disease or exacerbation of preexisting conditions with suspected or confirmed influenza.
  3. Baloxavir, oseltamivir, peramivir, or zanamivir may be used in uncomplicated outpatients suspected or confirmed to have influenza.
  4. Amantadine and rimantadine are not recommended for treatment in the United States due to high resistance.
• RSV and parainfluenza:
  1. Ribavirin aerosol may be effective for severe RSV pneumonia.
  2. No approved antiviral therapy for parainfluenza virus pneumonia.
• Human metapneumovirus: No specific antiviral treatment is available.
• Adenoviruses: No approved antiviral therapy for adenovirus; cidofovir has been used in severe cases.
• Varicella:
  1. Patients over age 12 yr who develop chickenpox should be treated with acyclovir or valacyclovir, which may prevent the development of pneumonia.
  2. Varicella pneumonia can be treated with IV acyclovir.
• Measles:
  1. No effective antiviral agent.
  2. Vitamin A should be given to children with measles.
• CMV:
  1. Acyclovir, ganciclovir, and valganciclovir are used to prevent CMV infection in transplant recipients.
  2. Ganciclovir and foscarnet, with or without CMV hyperimmune globulin, are used to treat CMV infection, including pneumonia.

• Supportive therapy is useful.
• Death is possible during acute illness.
• Residual functional abnormalities may be persistent or develop into or predispose to chronic respiratory diseases later in life.
• Morbidity and mortality rates after most viral pneumonias are increased by bacterial superinfection.

• To infectious disease specialist and/or pulmonologist if uncertainty about the diagnosis.
• If symptoms or findings are progressive, with severe respiratory compromise, diffuse infiltrates, or the development of ARDS, referral for supportive care on extracorporeal life support could be considered in select patients.

• Facial coverings, social distancing, and quarantine are important in reduction of COVID-19 transmission, which is spread by droplets and aerosols.
• Influenza spreads through close contact and by small droplets transmitted by cough.
• RSV is effectively transmitted by fomites and by direct contact (little by aerosol).
• Varicella is transmitted by direct contact or by aerosol.
• Of the three major forms of parainfluenza viruses (types 1 to 3), type 3 is the most common cause of viral pneumonia; types 1 and 2 primarily cause laryngotracheitis.
• Human metapneumovirus is a common cause of upper respiratory infections and pneumonia.

Viral Pneumonia (Patient Information)

Cytomegalovirus Infection (Related Key Topic)

Influenza (Related Key Topic)

Varicella (Related Key Topic)

COVID-19 Disease (Related Key Topic)