ATLANTA—On August 14, 2002, a worker at an oil refinery in Crawford County, Illinois, reported to the refinery’s health unit with a cough that had lasted two weeks.[1] On the same day, the worker’s supervisor reported a paroxysmal cough that had lasted three days and included an episode of cough syncope. In both patients, serology indicated recent infection with Bordetella pertussis, and thus the Crawford County Health Department (CCHD) was contacted.

The CCHD and the Illinois Department of Public Health (IDPH) began active surveillance and case investigations. At the oil refinery, workers reporting a cough illness were referred to the local community hospital for evaluation and were interviewed by CCHD and IDPH staff to determine the time of illness onset, area of work in the refinery, work schedule, and close contacts. In addition, local school officials and community health care providers were given guidelines on pertussis case recognition, reporting, and preventive measures.

In the course of about two months, 15 of 150 workers at two separate complexes in the refinery were diagnosed with pertussis. All had had contact with the aforementioned supervisor. Through enhanced case finding, 24 cases of pertussis were identified at the refinery or in the nearby community by December 13, 2002; 21 of the cases occurred in adults 20 or older.

Seventeen of the pertussis cases were associated with the oil refinery, and seven occurred among community members with no apparent relation to the refinery. All patients received macrolide antibiotics and were encouraged to undergo pertussis testing via polymerase chain reaction; nasopharyngeal samples were also cultured in many cases. With the cooperation of the refinery management, 150 close contacts of the 17 case patients were given azithromycin prophylaxis.

Since October 9, 2002, no new cases of pertussis have been reported.

INCIDENCE INCREASING

Immunity from childhood vaccination declines five to 15 years after the last pertussis vaccine dose, which may explain the increased incidence in adults and adolescents. In 1980, there were 1,730 cases of pertussis reported. In 2002, there were 8,296 cases. In fact, the incidence rate of pertussis among adults increased 400% between 1990 and 2001, and it is the only disease for which universal vaccination is recommended that has increased in incidence during the past 20 years.

Pertussis is highly contagious, especially during the first three weeks of infection, and can spread to exposed infants, who have the highest rates of complications and death. Unfortunately, in adults the disease is often overlooked in the diagnosis of cough illness. Adults with pertussis can have mild symptoms and may not seek medical attention. In the outbreak that occurred at the refinery, pertussis was not considered until the supervisor reported cough syncope.

Acellular pertussis vaccines are licensed for use in infants and children ages 6 weeks to 7 years. However, these vaccines may have a future role to play in preventing pertussis in older age-groups as well.

—Gale Jurasek

Reference
1. Pertussis outbreak among adults at an oil refinery—Illinois, August-October 2002. MMWR Morb Mortal Wkly Rep. 2003;52:1-4.

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