TABLE 21-8.

Clinical Features of Pneumonia in Infants Younger than 3 Months

	Respiratory Syncytial Virus	Other Respiratory Viruses	Chlamydia trachomatis	Cytomegalovirus	Pertussisa
History
Season	Winter	Unique to each	Any	Any	Any; peak July–October
Onset	Acute, days	Acute, days	Insidious	Insidious	Progressive, days
Illness in others	URI	URI, “flu,” croup	No	No	Cough
Fever	Half of cases	Majority of cases	No	Unusual	No
Cough	Yes	Yes	Yes/staccato	Yes	Yes/paroxysmal
Associated features	Apnea, URI	URI, croup, conjunctivitis	Conjunctivitis (prior or current)	Failure to thrive, hepatosplenomegaly	Apnea, cyanosis, posttussive vomiting
Physical examination
Predominant feature	Respiratory distress	Respiratory distress	Cough	Failure to thrive	Cough
General appearance	Ill, not toxic	Ill, not toxic	Well, tachypneic	Chronically ill	Well between paroxysms
Degree of illness: respiratory findings	Degree of illness = findings	Degree of illness = findings	Findings > degree of illness	Ill general appearance > respiratory illness	Ill only during cough
Auscultation	Wheezes, coarse crackles	Crackles, wheezes	Diffuse crackles	Crackles, ± wheezes	Clear
Laboratory studies
Chest radiograph	Hyperaeration, sub-segmental atelectasis	Hyperaeration, ± peribronchial thickening, ± diffuse interstitial infiltrates	Hyperaeration, diffuse alveolar and interstitial infiltrates	Diffuse interstitial infiltrates	Normal or perihilar infiltrate
White blood cell count	Normal or lymphocytosis	Normal, lymphocytosis, neutropenia	Eosinophilia	Normal, eosinophilia, lymphocytosis neutropenia	Lymphocytosis; eosinophilia unusual
Other findings	Hypoxemia		Increases in IgG, IgA, IgM	Increases in IgG, IgA, IgM; thrombocytopenia
Diagnostic tests	Nasal wash EIA, DFA, PCR, culture	Nasal wash EIA, DFA, PCR, culture	Conjunctival, NP DFA, EIA	Throat, bronchoscopy, lung biopsy, or urine culture	NP DFA, culture, PCR

DFA, direct fluorescent antibody (test); EIA, enzyme immunoassay; Ig, immunoglobulin; NP, nasopharyngeal specimen; PCR, polymerase chain reaction; URI, upper respiratory tract infection.

^aPertussis is included in this table because it should be considered in young infants with cough and respiratory distress, although pneumonia is characteristically absent.