Viruses of atypical PNA

Question 1

Overview of viral PNA

Answer 1

• Chief cause of viral PNA in adults are influenza A and B (>50% of adult viral PNA), adenovirus, parainfluenza virus, and RSV (respiratory syncytial virus)
• Pts who are immunocompromised most at risk for viral PNA, particularly from CMV, VZV, HSV, measles, and adenoviruses
• Children most commonly get RSV PNA

Question 2

General differences in findings btwn viral and bacterial PNA

Answer 2

• Viral more often in children/infants (think RSV), and bacterial PNA more common in adults
• Viral onset is more slow, bacterial onset is rapid
• Clinical differences: rhinitis and wheezing in viral, high fever and tachypnea in bacterial
• CXR: interstitial infiltrates bilaterally for viral (atypical) and lobar consolidation for bacterial (typical)

Question 3

Bacterial PNA (strep pneumo)

Answer 3

• Brief duration of Sx: fever, chills, fatigue, cough, chest pain
• Sputum sample contains PMNs and bacteria
• CXR shows focal consolidation

Question 4

Fungal PNA (PCP)

Answer 4

• Sx are slow progression: SOB, fever, non-productive cough, hypoxemia
• CXR shows bilateral diffuse infiltrates, but normal CXR common
• Often seen in HIV/immunosuppresed
• If they have HIV think PCP/CMV

Question 5

Differential for viral PNA

Answer 5

• Immunosuppressed pts have increased risk
• Influenza: CXR variable but usually diffuse interstitial process, sometimes lobar infiltrates/consolidation and pleural effusion
• CMV: more common in Tx/HIV pts, CXR usually diffuse
• Adenovirus: CXR shows patchy ground-glass infiltrates predominantly in lower lungs (associated w/ crowded living spaces and causing ARDS in military recruits)

Question 6

RSV

Answer 6

• The most important respiratory pathogen in infancy and childhood
• In adults it can cause mild respiratory infection
• Most common cause of bronchiolitis among infants and children under age 1
• RSV is highly contagious, and most infants exposed are ASx but some become very ill
• Infection with RSV is seasonal