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The World Health Organization estimated in 2002 that nearly 300,000 children died from pertussis.1 In the United States, in spite of widespread vaccination there has been a steady rise in the number of pertussis cases reported to the Centers for Disease Control and Prevention (CDC) over the past the last decade, punctuated by several statewide outbreaks in 2004 and 2005.2-5

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Epidemiology

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Pertussis occurs year-round in the United States, although the disease peaks in the summer and fall in most locations. Humans are the only reservoir for Bordetella pertussis, and transmission from person to person occurs via respiratory droplets. Attack rates following household exposure have been reported as high as 90% for unimmunized children.6-8 Attack rates in adult household contacts are at least 30%.6 Communicability is highest early in the disease, but may persist for weeks in some individuals.8 Unrecognized disease serves as a reservoir for spread of infection.

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Infants younger than 6 months of age have the highest burden of disease.9 Hospitalizations and mortality from pertussis are highest in infants under 3 months of age.10 Passively acquired transplacental antibodies afford little protection, and vaccine-induced immunity requires multiple immunizations. Based on CDC surveillance data from 2000 to 2003, 86% of hospitalizations for pertussis occur in infants less than 3 months of age.10 Apnea and respiratory distress were the most frequent complications, followed by pneumonias. Mortality is greatest in infants less than 3 months of age. The frequency of complications decline with increasing age; however, protracted cough (> 3 months), sleep disturbances, and weight loss are common in adults with pertussis; subcutaneous emphysema, pulled muscles, and even broken ribs may occur in adults following paroxysmal coughing.11,12

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In 2006 in the United States, infants younger than 6 months old had the highest reported rate of pertussis (84.21 per 100,000 population), but adolescents aged 10 to 19 years and adults older than 20 years contributed the greatest number of reported cases.4 The characteristic “whoop” is often absent in older individuals. It is not until the nagging, forceful cough has persisted for 2 or more weeks that adolescents and adults come to medical attention. Even then, diagnosis may be delayed or disease may go unrecognized because of a low index of suspicion.13 Adult caretakers with undiagnosed pertussis are frequently found to be the source for pertussis in infants.14 Nosocomial spread by health care workers has been well documented.15,16

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Bordetella are small, fastidious, aerobic gram-negative coccobacilli that require enriched media for isolation. B pertussis is a respiratory pathogen of humans only and is the sole cause of epidemic pertussis. B parapertussis is a closely related species that accounts for less than 5% of clinical pertussis.17B bronchiseptica occasionally causes disease in the immunocompromised host but is better recognized as a veterinary pathogen.18 Only B pertussis elaborates pertussis toxin....

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