The Daily Differential — Saturday, August 1, 2026

Pertussis

Pertussis can cause apnea, hypoxemia, pneumonia, and death in young infants while appearing deceptively mild in older children and adults. Early recognition protects vulnerable contacts and prevents prolonged transmission.

By the Blue Fish Med Desk Aug 1, 2026 · Phoenix

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A 7-year-old girl sits upright on the stretcher, cheeks flushed, eyes watering after a coughing spell that ends with a loud inspiratory gasp. Her mother reports that the episodes come in clusters, often followed by vomiting, while between spells the child looks surprisingly comfortable. The cough has lasted nearly three weeks, and tonight she briefly stopped breathing during one episode. The next decision has not yet been made.

— What’s your move? Read on.

Before you read

Who needs immediate respiratory support or admission?
When do antibiotics alter the patient’s course versus mainly interrupt transmission?

When to Think of It

Think pertussis with paroxysmal cough, inspiratory “whoop,” post-tussive emesis, cough-related syncope, or apnea—especially cough lasting ≥2 weeks without another explanation. The whoop may be absent in vaccinated patients, adolescents, adults, and infants; infants may present primarily with apnea, cyanosis, poor feeding, or bradycardia.

Sick or Not Sick

The key fork is adequate ventilation and oxygenation versus impending respiratory failure. Admit or escalate immediately for apnea, cyanosis, recurrent desaturation, exhaustion, pneumonia, dehydration, inability to feed, altered mental status, or young age—particularly infants <3 months.

The First Fifteen Minutes

Place the patient on droplet precautions; use continuous pulse oximetry and cardiorespiratory monitoring if apnea, hypoxemia, or young age is present.
Apnea, hypoxemia, or respiratory distress → oxygen by nasal cannula 1–6 L/min, titrated to age-appropriate saturation, because increased inspired oxygen corrects hypoxemia while the airway and ventilatory pattern are assessed.
Persistent apnea or inadequate ventilation → bag-mask ventilation with 100% oxygen, then prepare for intubation; ventilation, not simply oxygen, is required when the patient cannot move air.
Confirmed or strongly suspected disease, or high-risk exposure → azithromycin 500 mg PO on day 1, then 250 mg PO daily on days 2–5; it reduces nasopharyngeal bacterial burden and transmission, although it may not shorten an established cough. For infants and children, use 10 mg/kg PO on day 1, then 5 mg/kg PO daily on days 2–5; verify pediatric maximums and local protocol.
Unable to take oral therapy → azithromycin 500 mg IV daily in adults; pediatric IV dosing is weight-based and should be checked in a pediatric reference.
Severe bronchospasm with objective wheezing → albuterol 2.5 mg nebulized, because reversible bronchospasm may contribute to distress; routine bronchodilators do not treat the infection.
Obtain nasopharyngeal PCR or culture, but do not delay isolation or treatment when the clinical suspicion is high.

Definitive Care & Disposition

Send nasopharyngeal PCR during the first 3–4 weeks of cough; culture is more specific but less sensitive and is most useful early. Treat household and other high-risk close contacts with an age-appropriate macrolide, regardless of vaccination status, in consultation with public health. Keep the patient away from school, childcare, and healthcare settings until 5 days of effective antibiotics are completed, or 21 days from cough onset if untreated. Admit infants with apnea, cyanosis, feeding difficulty, hypoxemia, or recurrent paroxysms; ICU care is appropriate for recurrent apnea, escalating oxygen needs, pulmonary hypertension, or ventilatory failure.

How This One Kills

The dangerous miss is dismissing an infant’s apnea or cyanosis as reflux or a brief resolved unexplained event while paroxysmal pertussis causes recurrent hypoxemia, bradycardia, and sudden deterioration.

The Differential — What Else Looks Like This

Viral bronchiolitis — diffuse wheeze/crackles and persistent increased work of breathing rather than discrete cough paroxysms; confusing them can delay droplet isolation and contact prophylaxis.
Croup — barky cough and stridor, especially at night; confusing it can obscure a prolonged paroxysmal illness without upper-airway obstruction.
Asthma — expiratory wheeze and variable airflow limitation; confusing it can lead to repeated bronchodilators while transmission continues.
Foreign body aspiration — abrupt onset, focal wheeze, or unilateral air trapping; confusing it can delay bronchoscopy.

The Second-Day Story

In vaccinated adolescents and adults, the whoop may disappear and the illness may look like an unexplained cough lasting several weeks, sometimes with rib pain, vomiting, or syncope. In infants, the cough may be minimal or absent; apnea, cyanosis, poor feeding, or episodic bradycardia is the signal. Ask specifically about vaccination, household cough, school or childcare exposure, and cough duration, then use PCR early enough that a negative late test is not overinterpreted.

Back to Our Patient

Back to the 7-year-old girl with three weeks of paroxysmal cough, post-tussive vomiting, and a brief apnea episode: the pattern makes pertussis recognizable even without dramatic lung findings. Her oxygenation, work of breathing, hydration, mental status, and recurrence of apnea determine risk; if she is currently stable, obtain nasopharyngeal PCR, place her on droplet precautions, and give azithromycin 500 mg PO today followed by 250 mg daily for four days. Because she has had apnea, she warrants monitored observation or admission rather than routine discharge, with escalation to assisted ventilation if apnea or hypoxemia recurs; household contacts need public-health-directed prophylaxis.

Patient Presentation to Attending

How you’d present this patient on the floor — tight, pertinent positives and negatives, no rambling

“This is a previously healthy 7-year-old girl with three weeks of progressively paroxysmal cough, post-tussive emesis, and a brief apneic episode tonight. She has had no persistent fever, focal chest pain, or known aspiration event, but her mother reports a loud inspiratory gasp after several coughing fits and a coughing illness in a household contact. She is currently alert with normal work of breathing between spells, but had transient desaturation during observation and has no focal wheeze or unilateral breath sounds. My leading diagnosis is pertussis with apnea risk, with viral infection, asthma, and foreign body aspiration as alternatives. I would place her on droplet precautions, obtain nasopharyngeal PCR, start azithromycin, monitor continuously, and admit for recurrent apnea or desaturation surveillance.”

Study Directive

From memory, list the three phases of pertussis and the typical timing of PCR versus culture.
Practice calculating adult and pediatric azithromycin regimens.
Review local public-health criteria for postexposure prophylaxis and return-to-school restrictions.
Work through three apnea cases and state the precise admission/ICU trigger for each.

Recent Literature

Review or guideline Expert consensus for pertussis in children: new concepts in diagnosis and treatment
Mi YM, Deng JK, Zhang T, et al. · World J Pediatr, 2024 · PMID 39537933 · cited 38×

Provides a current pediatric consensus on recognizing, confirming, and treating pertussis—especially important for infants at highest risk of apnea and severe disease.

Full text · open access

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Antibiotics and Pneumonia

Pneumonia is a common cause of respiratory failure and sepsis, but inappropriate antibiotic selection, delayed administration, and failure to identify...

Listen: EM:RAP podcast →

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The Case

A 68-year-old woman arrives with a winter coat still zipped to her chin, breathing fast enough that each sentence breaks into fragments. Her fingers are cool, her cough produces rust-colored sputum, and the pulse oximeter flashes 84% despite a nonrebreather mask. Her daughter says the patient was independent yesterday but became confused overnight. The antibiotic decision has not yet been made.

Before You Read

Which findings make pneumonia a sepsis emergency rather than a routine infection?
What empiric regimen fits the patient’s setting and risk factors?
When does “aspiration” require anaerobic coverage—and when does it not?

Why It Matters

Pneumonia is a common cause of respiratory failure and sepsis, but inappropriate antibiotic selection, delayed administration, and failure to identify resistant pathogens all worsen outcomes. The right regimen is determined by severity, acquisition setting, comorbidity, and prior microbiology—not by the radiograph alone.

When to Think of It

Suspect pneumonia with acute cough, fever or hypothermia, dyspnea, pleuritic pain, sputum, hypoxemia, focal crackles, delirium, or a new infiltrate. Older adults may present with weakness, falls, anorexia, or confusion without fever or cough.

Sick or Not Sick

The key fork is adequate oxygenation and perfusion versus severe pneumonia with respiratory failure or sepsis. The single most important call is whether the patient needs immediate ventilatory support and sepsis-level resuscitation, not whether the infiltrate is “large.”

The First Fifteen Minutes

Hypoxemia → nasal cannula 1–6 L/min, escalating to a nonrebreather at 10–15 L/min or high-flow nasal oxygen per local protocol; oxygen restores the diffusion gradient while definitive therapy begins.
Persistent hypoxemia with increased work of breathing but preserved airway protection → high-flow nasal cannula, because it delivers more reliable FiO₂ and modest positive pressure.
Severe community-acquired pneumonia requiring ICU admission → ceftriaxone 2 g IV once daily plus azithromycin 500 mg IV once daily, covering typical bacteria and atypical pathogens; give promptly after cultures if this does not create a meaningful delay.
Severe immediate beta-lactam allergy → levofloxacin 750 mg IV once daily as an alternative; fluoroquinolone selection requires attention to QT prolongation, tendinopathy, aortic risk, and local resistance.
Risk for MRSA—prior MRSA respiratory isolation, recent hospitalization with IV antibiotics, or severe necrotizing/post-influenza pattern—→ vancomycin 15–20 mg/kg IV once, then pharmacy-guided dosing, because it covers resistant gram-positive disease. Dose and monitoring vary with renal function; check an institutional protocol.
Risk for Pseudomonas or hospital-acquired infection—recent IV antibiotics, structural lung disease, prior Pseudomonas, or hospitalization-associated pneumonia—→ cefepime 2 g IV every 8 hours or piperacillin-tazobactam 4.5 g IV every 6 hours, because antipseudomonal beta-lactam coverage is required. Adjust for renal function and local antibiogram.
Septic shock or hypoperfusion → balanced crystalloid 30 mL/kg IV, with frequent reassessment for overload; fluid restores circulating preload but should not be given blindly in severe cardiac or renal failure.
Persistent hypotension after fluids → norepinephrine 0.05–0.1 mcg/kg/min IV infusion, titrated to a MAP generally ≥65 mmHg, because alpha-adrenergic vasoconstriction restores perfusion with less tachyarrhythmia than dopamine.
Aspiration with abscess, empyema, or severe periodontal disease → ampicillin-sulbactam 3 g IV every 6 hours; routine anaerobic coverage is not required for uncomplicated aspiration pneumonia without these features.

Definitive Care & Disposition

Obtain blood cultures and a good lower-respiratory specimen in severe disease or when resistant organisms are suspected, but do not delay antibiotics for difficult collection. Use lactate, renal function, blood gas when indicated, imaging, and repeated examination to guide severity. Narrow therapy when cultures and clinical response permit; uncomplicated CAP often receives a minimum of about 5 days with clinical stability before stopping, while empyema, abscess, bacteremia, or resistant pathogens require longer specialist-guided courses. ICU indications include mechanical ventilation, vasopressors, severe hypoxemia, shock, or multiple minor severity criteria. Drain empyema and address obstruction or foreign material—antibiotics alone are inadequate source control.

How This One Kills

The critical miss is treating the radiograph while overlooking respiratory fatigue: a patient with escalating oxygen needs and altered mentation can progress from “pneumonia” to arrest while repeated antibiotic adjustments distract from intubation or source control.

The Atypical Presentation

Older adults, immunocompromised patients, and those with renal disease may be afebrile and have only delirium, weakness, tachypnea, or hypoxemia. A normal white count does not reassure, and a single portable radiograph may undercall early or posterior disease. Let respiratory rate, oxygen requirement, perfusion, mental status, and trajectory drive urgency; use microbiology and response to refine—not replace—the initial clinical judgment.

Back to Our Patient

Back to the 68-year-old woman with fragmented speech, confusion, cool extremities, and oxygen saturation of 84% on a nonrebreather: she has severe pneumonia with impending respiratory failure and possible septic shock. Risk stratification, not the sputum color, drives the next move—prepare for intubation or escalation of respiratory support, obtain cultures if immediately feasible, give balanced crystalloid with reassessment, and start ceftriaxone 2 g IV plus azithromycin 500 mg IV without delay. If hypotension persists after fluids, begin norepinephrine; assess for MRSA or Pseudomonas risk before adding vancomycin or an antipseudomonal agent. She requires ICU admission, with de-escalation and evaluation for empyema or another source as data return.

Patient Presentation to Attending

“This is a 68-year-old woman with abrupt cough, rust-colored sputum, dyspnea, and new confusion, now tachypneic with an oxygen saturation of 84% on a nonrebreather. She has no known aspiration event, unilateral leg swelling, or preceding orthopnea, but her daughter reports rapid decline from baseline. She is cool, speaks in fragments, and has focal right basilar crackles with persistent hypoxemia. I am concerned for severe community-acquired pneumonia causing acute hypoxemic respiratory failure and sepsis, with pulmonary embolism and cardiogenic edema as alternatives. I would prepare for definitive airway management, obtain cultures and lactate without delaying therapy, administer ceftriaxone and azithromycin, give carefully reassessed crystalloid, start norepinephrine for persistent shock, and admit her to the ICU.”

Study Directive

Build empiric regimens for nonsevere CAP, severe CAP, aspiration pneumonia, HAP, MRSA risk, and Pseudomonas risk.
Memorize ceftriaxone/azithromycin doses and the triggers for adding vancomycin or antipseudomonal coverage.
Practice recognizing when pneumonia requires intubation, vasopressors, drainage, or ICU admission.
Review your institution’s antibiogram and antibiotic de-escalation policy.

Key Medications

Ceftriaxone: 2 g IV every 24 hours.
Azithromycin: 500 mg IV or PO daily.
Levofloxacin: 750 mg IV or PO daily; adjust for renal function and check QT-risk factors.
Vancomycin: 15–20 mg/kg IV loading dose, then pharmacy/AUC-guided dosing; meaningful variability requires an institutional protocol or Lexicomp/UpToDate.
Cefepime: 2 g IV every 8 hours for severe antipseudomonal coverage; renal adjustment is essential.
Piperacillin-tazobactam: 4.5 g IV every 6 hours; extended-infusion and renal-adjusted regimens vary by institution.
Ampicillin-sulbactam: 3 g IV every 6 hours for aspiration pneumonia with anaerobic-risk features.
Norepinephrine: start 0.05–0.1 mcg/kg/min IV and titrate to perfusion/MAP.
Pediatric pneumonia regimens are weight-based and differ substantially; consult a pediatric reference.

High-Yield Pearls

Oxygen requirement and work of breathing are often more prognostic than fever or leukocytosis.
“Aspiration” is an event; anaerobic coverage is a decision based on abscess, empyema, necrosis, or severe dental disease.
Broad therapy should have an exit plan: obtain cultures when indicated and narrow once the pathogen and clinical trajectory are clear.

The Mimics

Pulmonary embolism — disproportionate dyspnea, pleuritic pain, or hypoxemia with a minimal infiltrate; confusing it can delay anticoagulation or reperfusion therapy.
Cardiogenic pulmonary edema — orthopnea, diffuse B-lines, edema, and cardiac history; confusing it can worsen volume overload with unnecessary fluids.
Atelectasis — volume loss and rapid radiographic change; confusing it can cause unnecessary broad-spectrum antibiotics.
Organizing or inflammatory pneumonitis — subacute symptoms with poor antibiotic response; confusing it can delay immunomodulatory or specialty evaluation.

Board Question

A 74-year-old man develops pneumonia after vomiting during a seizure. He is febrile and hypoxemic, with a dependent-lobe infiltrate but no abscess, empyema, severe periodontal disease, or putrid sputum. Which empiric regimen is most appropriate?

ACeftriaxone plus metronidazole solely because aspiration occurred
BAmpicillin-sulbactam or a standard CAP regimen based on severity
CVancomycin monotherapy
DClindamycin monotherapy for all aspiration events

Reveal answer

Correct: B

Aspiration pneumonitis and uncomplicated aspiration pneumonia do not automatically require additional anaerobic coverage. Add dedicated anaerobic therapy when abscess, empyema, necrosis, or major periodontal disease is present.

Recent Literature

Review or guideline Diagnosis and Management of Community-acquired Pneumonia: An Official American Thoracic Society Clinical Practice Guideline
Am J Respir Crit Care Med, 2026 · cited 62×

Use this updated ATS guideline to guide empiric antibiotic selection, diagnostic testing, and treatment decisions for adults with community-acquired pneumonia.

TheDaily Differential

Pertussis

When to Think of It

Sick or Not Sick

The First Fifteen Minutes

Definitive Care & Disposition

How This One Kills

The Second-Day Story

Study Directive

Recent Literature

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