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in the initial regimen. Standard precautions should be used for patients with lung abscesses unless tuberculosis is
suspected (in which case, airborne precautions should be implemented).
Pertussis
Pertussis (whooping cough) is caused by Bordetella pertussis or Bordetella parapertussis (the latter being the
cause of kennel cough in dogs). There were an estimated 19,000 cases in 2017, with approximately 80% occurring
in children (and almost 10% occurring in infants younger than 6 months). A similar clinical syndrome can be
caused by adenovirus or Chlamydia trachomatis in infants. There are three clinical stages. The first symptoms are
indistinguishable from a viral URI. This catarrhal phase, characterized by a mild cough, conjunctivitis, and coryza,
lasts for 1 to 2 weeks. An increasingly severe cough heralds the onset of the second stage (paroxysmal), which
continues for 2 to 4 weeks. After a prolonged spasm of coughing often involving 10 or more coughs in succession,
the sudden inflow of air produces the characteristic whoop (young infants lack the ability to generate sufficient
negative inspiratory pressure and may, therefore, not whoop). During episodes, children can appear to choke,
become cyanotic, and appear anxious. Post-tussive emesis is common. When not coughing, the child has a
remarkably normal history and physical examination, except for an occasional subconjunctival hemorrhage. Young
infants can exhibit apnea unrelated to coughing paroxysms. During the third stage (convalescent), the intensity of
the cough wanes. At times, pertussis may present as a chronic cough without other signs of infection. The fatality
rate for pertussis is approximately 1% for patients in the first month of life and 0.3% for those between age 2 and
12 months. Complications often occur during the paroxysmal stage. The most immediately life-threatening
complication is complete obstruction of the airway by a mucous plug, leading to respiratory arrest. Secondary
bacterial pneumonia occurs in 25% of children with pertussis and accounts for 90% of the fatalities. Seizures are
seen in 3%, and encephalitis in 1%. Sudden increases in intrathoracic pressure can cause intracranial hemorrhages,
rupture of the diaphragm, and rectal prolapse.
The white blood count often is elevated, at times with a leukemoid reaction (the latter more common in infants
over 6 months of age) and a lymphocytic predominance. Chest radiographs often are normal. The diagnosis is by
PCR of nasopharyngeal secretions. Early treatment can reduce symptoms and shorten the clinical course although
it is unclear if antibiotics influence course during paroxysmal phase (does still reduce transmission); however, it is
important to start antibiotic treatment when pertussis is suspected and prior to confirmatory testing. The preferred
treatment is azithromycin (10 mg/kg daily for 5 days in infants <6 months of age and 10 mg/kg daily on the first
day (maximum: 500 mg), followed by 5 mg/kg for the subsequent 4 days for older children, maximum 250 mg).
Erythromycin (40 mg/kg/day divided every 6 hours × 14 days, maximum dose: 2 g/day) can also be utilized,
though the more frequent dosing interval and longer treatment duration are associated with reduced adherence.

Household and close contacts (even if fully immunized) require chemoprophylaxis with azithromycin. Contacts
who are not fully immunized should also receive a booster dose of the vaccine (DTaP for children <7 years of age,
TDaP for children 7 years and above). Receipt of the acellular pertussis vaccine does not obviate the need for
postexposure prophylaxis (PEP) for healthcare workers, so strict use of droplet precautions (gloves, mask) is
needed for any provider caring for a child with suspected pertussis.

CARDIAC INFECTIOUS EMERGENCIES
Kawasaki Disease
See also:
Chapter 86 Cardiac Emergencies
Chapter 101 Rheumatologic Emergencies
CLINICAL PEARLS AND PITFALLS