http://www.emedicine.com/emerg/topic394.htm

Authored by Joseph Bocka, MD, Director, Department of Emergency Medicine, Med Central Health System

Joseph Bocka, MD, is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, and National Association of EMS Physicians

Edited by Garry Wilkes, MD, Director, Clinical Senior Lecturer, Department of Emergency Medicine, Bunbury Health Service; Robert Konop, PharmD, Pediatric Clinical Pharmacy Specialist Manager, Clinical Assistant Professor, Department of Clinical Pharmacy, University of Minnesota; Grace M Young, MD, Associate Professor, Department of Pediatrics, University of Maryland Medical Center; John Halamka, MD, Chief Information Officer, CareGroup Healthcare System, Assistant Professor of Medicine, Department of Emergency Medicine, Beth Israel Deaconess Medical Center; Assistant Professor of Medicine, Harvard Medical School; and William K Mallon, MD, Program Director, Internship Training, Associate Professor, Department of Emergency Medicine, University of Southern California

eMedicine Journal, February 23 2001, Volume 2, Number 2

Background: In the pre-vaccination era, pertussis (i.e., whooping cough) was a leading cause of infant death. Although the number of cases reported had dropped by more than 99% from the 1930s to the 1970s, a significant increase has been seen in the U.S. and Europe during the 1980s and 1990s. The disease still carries significant morbidity and mortality in infants less than 2 years of age. Pertussis should be included in the differential diagnosis of protracted cough with cyanosis or vomiting, persistent rhinorrhea, and marked lymphocytosis.

Pathophysiology: Bordetella pertussis is an aerobic, non-motile, gram-negative coccobacillus that attaches to and multiplies on the respiratory epithelium; starting initially in the nasopharynx and ending up, primarily, in the bronchi and bronchioles.

A mucopurulosanguinous exudate is formed in the respiratory tract. This compromises the small airways; especially, those of infants; and predisposes the affected individual to atelectasis, cough, cyanosis, and pneumonia.

The lung parenchyma and blood stream are not invaded; thus, blood cultures are negative.

Transmission is only from human-to-human via aerosol droplets. The disease is highly contagious, in that 80-90% of those exposed (who are susceptible) will develop the disease. Most cases occur in the late summer and early fall.

Frequency:

• In the US: In 1930, pertussis peaked, with 265,000 cases reported and over 7000 deaths in the U.S. This decreased to a low in 1976, when there were 1,010 cases with only 4 deaths. This has recently increased to about 5000 (i.e., 2 cases/100,000/y) cases reported annually to the CDC, with a peak of 6586 in 1993. These numbers are falsely low, as the CDC estimates that only 5-10% of pertussis cases are believed to be recognized and reported. Pertussis is the most commonly reported vaccine-preventable disease among children in the U.S. who are younger than 5 years of age.

In reported studies, 12-32% of adults with "prolonged cough" (1-4 wk) have been found to have pertussis.

• Internationally: In England, the percent vaccinated over the last 3 decades dropped to 30%. This has resulted in more than 10,000 cases being reported in the 1970s and 80s; with more than 200 deaths and 10,000 prolonged hospitalizations. Germany had a similar occurrence in the 1980s and 90s. This approaches the pre-vaccination era incidence. Recent similar epidemic outbreaks have occurred in Sweden, Canada, and Germany.

Mortality/Morbidity: Mortality formerly was greater than 50% in hospitalized patients; now the mortality rate for hospitalized patients in the U.S. and Europe is about 1/500 cases (0.2% of those reported).

• Most die from secondary pneumonia (90-95% of deaths) dehydration, hypoxia, encephalopathy, or cerebral hemorrhage. Cerebral hemorrhage occurs secondary to paroxysmal coughing which causes ICP to surge.

• Today, about 25% of those under age 4 years and 12%, overall, will secondarily develop a bacterial pneumonia. Approximately 2% will develop seizures, most of these being infants less than 6 months of age. These seizures are believed to be a result of hypoxia or cerebral hemorrhage from the prolonged coughing spells.

• Pertussis was a leading cause of death in the pre-vaccination era, peaking at more than 7,000 deaths reported in 1930 in the U.S. This reached a low of 4 reported deaths in 1982 and recently has risen to an average of about 25 deaths annually in the U.S.

Sex: Females are more common than males

Age:

• The predominant age is between 3 mo-6 y. More than 70% of the cases are in children under 6 y.

• Due to the lack of maternal immunity transfer, more than 35% of all cases occur in infants under 6 mo and more than 90% of all deaths occur in this same age group.

• The natural disease does not provide lifelong immunity, as earlier thought. Three injections of the (cellular or acellular) vaccine provide up to 12 y of protection. This helps account for the more than 10-fold increase reported in those over 18 y.

History:

• Classically, pertussis consists of 3 stages: Incubation, Catarrhal, and Paroxysmal.

• The asymptomatic incubation period is 7-10 d.

• The Catarrhal stage follows and lasts about 2-7 d.

• Minimal or no fever.

• Rhinorrhea.

• Anorexia.

• Mild but increasing cough.

• The Paroxysmal stage follows, lasting about 1-8 wk.

• It is characterized by paroxysms of coughing, provoked by feeding (in infants) and exertion.

• These are less spontaneous than in typical respiratory infections.

• The inspiratory gasp/whoop eventually develops, especially in those between 6 mo-5 y.

• Infants under 6 mo often vomit in association with the cough, which leads to dehydration.

• Hypoxia tends to be more severe than the clinical appearance of the child suggests.

• A significant number will present with cyanosis and apneic spells.

• Vaccinated adults usually only develop a prolonged bronchitis without a whoop. Unvaccinated adults are more likely to have whooping and post-tussive emesis.

• 12-32% of adults with persistent cough (greater than 2 wk) were found to have pertussis. On average they wait a median of 3 wk before seeking treatment.

Physical:

• The classic inspiratory gasp/whoop primarily develops in those between 6 mo-5 y. It is usually absent in those under 6 mo and in most older, vaccinated children and adults; however, it can often be seen in unvaccinated adults, as can post-tussive emesis.

• Hypoxia should be considered.

• Dehydration is common on presentation.

• Mild fever. Fever over 39 degrees C is rare.

Causes:

• Bordetella pertussis.

• Bordetella parapertussis and Bordetella bronchiseptica are less common and produce a similar but milder clinical illness.

• Risk Factors:

• Nonimmunized children.

• Contact with an infected person.

• Epidemic exposure.

• Pregnancy.

Asthma
Bronchitis
Chronic Obstructive Pulmonary Disease and Emphysema
Encephalitis
Gastroenteritis
Pediatrics, Bronchiolitis
Pediatrics, Croup or Laryngotracheobronchitis
Pediatrics, Crying Child
Pediatrics, Dehydration
Pediatrics, Febrile Seizures
Pediatrics, Fever
Pediatrics, Gastroenteritis
Pediatrics, Intussusception
Pediatrics, Pertussis
Pediatrics, Tachycardia
Pneumonia, Aspiration
Pneumonia, Bacterial
Pneumonia, Mycoplasma
Pneumonia, Viral
Tuberculosis

Other Problems to be Considered:

• Common Cold
• Adenoviral Syndromes
• Influenza
• Cystic Fibrosis
• Interstitial Pneumonitis
• Foreign Body

Lab Studies:

• In children, lymphocytosis is often profound (greater than 70% of the total WBC count). The WBC count often rises to 20-40,000 cells/mm₂; and up to 100,000. In adults, especially those vaccinated, this finding is rare.

• Definitive culture diagnosis is not always possible.

• Blood cultures uniformly are negative.

• An immediately plated, deep, nasopharyngeal swabbing grown for 1 week in Bordet-Gengou agar classically is considered to be the gold standard of diagnosis. However, it is only believed to be positive 15-40% of the time and gives results too late for clinical usefulness.

Imaging Studies:

• Chest x-ray (CXR):

• Focal atelectasis.

• Peribronchial cuffing.

Other Tests:

• Direct Fluorescent Antibody (DFA) studies immediately performed from nasopharyngeal samples are positive in 40-80% of cases. Currently, the DFA studies provide the majority of case confirmations along with a consistent history.

• Results can be available within minutes.

• Specimens should be obtained within the first 3 weeks of the disease (i.e., in incubation, catarrhal or early paroxysmal stages).

• Serologic testing, using ELISA techniques, is now considered by many to be the gold standard.

Emergency Department Care:

• General supportive measures (e.g., oxygen, breathing treatments, and mechanical ventilation, as needed).

• Careful observation for apnea, cyanosis, or hypoxia in infants.

• Isolation from susceptible patients (especially infants) for 4 weeks; especially until 1 week of antibiotic therapy is completed.

• Admission Considerations:

• Under 1 year of age.

• Pneumonia.

• Apneic or cyanotic spells.
• Moderate to severe dehydration.

• Prophylaxis: The effectiveness, of prophylaxing exposed, susceptible persons, has not been determined; however, it is recommended for household and close contacts.

• Erythromycin 50 mg/kg/d divided qid x 14 d.

• Clarithromycin (as an alternative whose effectiveness has not been proven, but it is inferred) 7.5 mg/kg bid x 14 d

Consultations: Pertussis is a reportable infectious disease in the U.S.

Drug Category: Antibiotics - Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.

Deterrence/Prevention:

• Whole Cell Vaccine

• The vaccine, used from the 1940s until the mid 1990s in the U.S. and from the 1940s until the 1980s in Europe, consisted of a whole cell with endotoxin given in 4 doses. Eighty percent acquired effective protection with this regimen. Two doses provided some immunity, while one dose alone was of little protection.

• Due to this lack of initial protection, infants experience the majority of the cases, morbidity and mortality.

• Full immunity lasts for 3 years and rapidly falls to essentially providing no protection after 12 years. The natural disease, originally thought to provide lifelong protection, has been found to lessen the course of subsequent disease.

• A local reaction is reported in 50%; seizure without fever in one per 1750, encephalitis in 10.5 per million and permanent brain damage rare. Concern over CNS side effects is a major reason for many choosing not to be vaccinated.

• Acellular Vaccine

• Vaccination is now recommended with an acellular vaccine at 2, 4, 6, and 15-18 months of age with a booster at 4-6 years of age.

• Following acellular vaccine immunization, fever was reported in 3-5%; persistent crying in 12/100,000; febrile seizures in 5/100,000; afebrile seizure in 2/100,000 and hyporesponsive episodes in 5/100,000. Severe neurologic sequelae have not been reported.

• High-risk health care providers and adults should consider a booster immunization with an acellular vaccine every 10 years.

Complications:

• Pneumonia.

• Hypoxic encephalopathy.

• Otitis media.

• Tuberculosis activation.

• Epistaxis, hemoptysis.

• Hernia.

• Re-induction of paroxysmal coughing with upper respiratory infections.

• Seizures.

• Cerebral hemorrhage.

• Coma and death.

Prognosis:

• With treatment, complete recovery is expected.

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eMedicine Journal, February 23 2001, Volume 2, Number 2
© Copyright 2001, eMedicine.com, Inc.

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