Background

During the first week of August 1998, the Communicable Disease Control Program was contacted by one of Utah’s 12 local health districts to report three cases of pertussis among staff at a local hospital. Thirty-four cases of pertussis had been reported to the Bureau of Epidemiology to date for 1998 and six of those cases were among adults (this includes three 1997 cases reported in 1998). At that time the Utah Immunization Program assisted with a newsletter article "Pertussis Persists in Children and Adults," (Epidemiology Newsletter, July 1998) to provide an update on pertussis in Utah and to encourage health care providers to consider pertussis in both children and adults who present with a cough illness.

Investigation

Since the first of July 1998, 26 children have been hospitalized with symptoms consistent with pertussis. Seven of the children hospitalized were from a rural area of the state. Their ages ranged from three months to three years with four of these patients under the age of six months. The other 19 children were hospitalized in Salt Lake County and their ages ranged from two weeks to two years. No adults have been hospitalized and no fatalities have been reported.

Ninety-one confirmed and 154 probable cases have been identified in addition to 217 suspect cases. Confirmed and probable cases are defined using the Centers for Disease Control and Prevention (CDC), MMWR Recommendations and Reports, May 2, 1997, "Case Definitions for Infectious Conditions Under Public Health Surveillance". Confirmed is defined as a case that is: 1) laboratory confirmed by isolation of Bordetella pertussis from a clinical specimen or a positive polymerase chain reaction for B. pertussis, or 2) one that meets the clinical case definition and is either laboratory confirmed or epidemiologically linked to a laboratory-confirmed case. The clinical case definition is a cough illness lasting > 2 weeks with one of the following: paroxysms of coughing, inspiratory "whoop", or post-tussive vomiting, without other apparent cause. A probable case is one that meets the clinical case definition, is not laboratory confirmed, and is not epidemiologically linked to a laboratory-confirmed case. For purposes of this outbreak, the Utah Department of Health is defining a suspect case as any cough illness of unknown etiology. Only confirmed and probable cases are included in the total case count. The ages of the cases have ranged from newborn to 72 years (Figure 1) with 61 of those less than one year of age. The dates of onset of illness have been grouped by month (Figure 2). The three cases that had onset dates in late 1997 and were not reported until 1998 are not included.

Figure 1

Figure 2

Staff from the Utah Department of Health traveled to the affected rural area to assist with the outbreak investigation. It appeared that the outbreak of pertussis had been ongoing since mid-July and was distributed through most of the community. An approach of targeted early case identification, prophylaxis of contacts, an accelerated immunization schedule for infants living in the affected area, and an aggressive education campaign was chosen as the most practical strategy of management. A separate pertussis monitoring surveillance system was initiated in order to: 1) rapidly assemble information on the current outbreak, 2) provide data sufficient to develop an epidemic curve, 3) determine the number of households with infectious members, 4) characterize compliance with recommendations for prophylaxis, and 5) determine the frequency of travel outside the community.

Along the Wasatch Front, which includes Salt Lake County, staff from the local health districts have identified cases and their contacts to provide prophylaxis and education. Many of the cases have been among large extended families who frequently associate with each other. This has assisted in locating contacts of cases to provide prophylaxis.

Transmission of pertussis may be reduced in household or close contacts by early treatment with an effective antimicrobial agent (Table 1). All household and other close contacts of a pertussis case should receive treatment, regardless of age and vaccination status. Patients in the early stages of infection and those with cough illness of less than three weeks duration should also be treated as soon as possible. For greatest efficacy, antibiotic therapy must be given early in the course of disease, preferably before the paroxysmal stage of the cough develops. Young children with symptoms suggestive of pertussis should be evaluated by a health care provider, provided with antibiotics and information on how to determine if a child should be reassessed and hospitalized for supportive care. Infants less than one year of age who demonstrate cough paroxysms with apnea and/or cyanosis should be hospitalized for supportive care and antibiotic therapy.

Table 1.

In order to continue to monitor the incidence of pertussis, cultures should be promptly collected on symptomatic individuals. The preferred specimen is a nasopharyngeal swab collected early in the course of illness. The later the culture is obtained (usually after 1-2 weeks), the less likely it is to be helpful in making the diagnosis.

We strongly encourage health care providers to continue to be suspicious of pertussis in anyone with a persistent cough or other symptoms consistent with pertussis. Please report cases or suspect cases to your local health department or to the Bureau of Epidemiology (801-538-6191).

Send comments to:
The Bureau of Epidemiology
Box 142104
Salt Lake City, UT 84114-2104
or call (801) 538-6191

Approval 8000008: Appropriation 3705