Pertussis on the Rise—Atypical Infections Increasingly Common
Abstract & Commentary
Source: Centers for Disease Control and Prevention. Pertussis—United States, 1997-2000. MMWR Morb Mort Weekly Rep 2002;51:73-76.
The Centers for Disease Control and Prevention tracks the number of pertussis cases reported by state departments of health on a weekly basis. A clinical case of pertussis is defined as an acute cough lasting at least 14 days when associated with paroxysmal coughing, post-tussive vomiting, or inspiratory whoop, or when associated with a known pertussis outbreak.
Between 1997 and 2000, 29,134 cases of pertussis were reported. Twenty-nine percent of cases were younger than age 1, 12% were 1-4 years old, 10% were 5-9 years old, 29% were 10-19 years old, and 20% were 20 years old or older. Among infants younger than 6 months old, 63% required hospitalization, 12% had pneumonia, and 1% had seizures. The incidence of hospitalization and other serious sequelae decreased dramatically with increasing age, although 4% of patients 20 years old and older required hospitalization and 5% developed pneumonia. Among all patients, there were 26 cases of encephalopathy and 62 pertussis-related deaths.
Compared to the 1994-1996 reporting period, the incidence of pertussis has increased 11% among infants, 62% among adolescents, and 60% among adults. While some of the increase in older patients may be due to better disease recognition, the increase among infants suggests a true rise in the incidence of pertussis.
Commentary by David J. Karras, MD, FAAEM, FACEP
Pertussis, commonly known as whooping cough, is a highly contagious bacterial respiratory illness. Prior to widespread use of vaccines in the 1950s, most children developed the disease. In 1934, more than 260,000 cases and 10,000 deaths were reported. By contrast, only 1010 cases were reported in 1976. The incidence of the disease began rising in the early 1980s, and in 1993 more than 6500 cases were reported.1
The increase in pertussis has been greatest in adolescents and adults. The immunity conferred by vaccination wanes within five to 10 years, leaving older age groups susceptible to infection. Disease in previously immunized individuals appears to be much milder than in infants, making it far more difficult to diagnose. Older patients do not present with the classic three-stage (catarrhal, paroxysmal, convalescent) illness. Their clinical course generally is mild, with protracted cough lasting several weeks. Several studies have suggested that 20-25% of adults with protracted coughs might have pertussis.2
Diagnosis is important, both because therapy can shorten the duration of illness and because adults are the primary source of infection to susceptible children, who have a high incidence of serious illness. Unfortunately, diagnosis requires specialized testing and generally falls outside the scope of practice for emergency physicians. We do, however, have an obligation to recognize the potential for pertussis in patients with protracted coughs and make appropriate referrals to primary care practitioners.
References
1. The Centers for Disease Control and Prevention (CDC). Pertussis vaccination: Use of acellular pertussis vaccines among infants and young children. Recommendations of the Advisory Committee on Immunization Practices. Summary. MMWR Morb Mort Weekly Rep 1997;46:1-25.
2. Yaari E, et al. Clinical manifestations of B. pertussis infection in immunized children and young adults. Chest 1999;115:1254-1258.
Dr. Karras, Associate Professor of Emergency Medicine, Department of Emergency Medicine, Temple University School of Medicine, Director of Emergency Medicine Research, Temple University Hospital, Philadelphia, Pa., is on the Editorial Board of Emergency Medicine Alert.
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