Bureau of Epidemiology
Bureau of Epidemiology November 1998 Utah Department of Health
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Pertussis Outbreak in Utah, 1998
Rheumatic Fever
Monthly Morbidity Summary

Pertussis Outbreak in Utah, 1998

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.

Four weeks later, 50 cases of pertussis had been reported in Utah for 1998 and hundreds of suspect cases had been identified in seven local health districts. The Utah Department of Health issued a state-wide pertussis alert and implemented active surveillance for pertussis. Many of the cases were occurring in populations that have traditionally had low immunization rates. By the end of November, 242 cases have been reported and many suspect cases are still under investigation.

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

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Figure 2

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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.

The Utah Public Health Laboratory initiated active surveillance in local health districts with at least one case of pertussis in an effort to look for adolescents and adults that may be carrying B. pertussis. In addition, the laboratory has Pulse Field Gel Electrophoresis (PFGE) capability that uses genetic fingerprinting to track the outbreak and compare these molecular patterns with what is being seen elsewhere in the U.S. Three patterns have been identified using PFGE. One of the patterns that is predominant in the rural area was also identified in one of the Salt Lake County cases that gave a history of travel to the rural site. Epidemiological linkages are still being investigated but we now know that more than one strain of pertussis is circulating in the state. From all the reporting laboratories including the State Public Health Laboratory, 48 cases have been confirmed by culture and 14 of those were in persons 13 years of age and older.

Recommendations

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.

RECOMMENDED ANTIBIOTIC REGIMENS*
First Line Therapy
Erythromycin (E-mycin, Erye, Ery-Tab)
Children 50 mg/kg per day divided qid x 14 days (maximum 2 gm/day)
Adults 50 mg/kg per day divided qid x 14 days (maximum 2 gm/day)
Alternative Regimens
Trimethoprim-Sulfamethoxazole (TMP/SMX, Bactrim, Septra); Dosing based on TMP
Children TMP 8 mg/kg per day divided bid x 14 days (Sanford 1996)
Adults 1 DS tab bid x 14 days
Pediazole (EES 200 mg/5cc + Sulfisoxazole 600 mg)
Children 50 mg/kg per day divided qid x 14 days (based on EES, with maximum 2gm/day)
Adults Not commonly used
Clarithromycin**
Children 15 mg/kg per day divided bid x 10 days
Adults 500 mg bid x 10 days
Azithromycin**
Children Not commonly used
Adults 500 mg day #1, 250 mg on days #2-10
Note:
* Antibiotic dosing and duration is the same whether prescribed for prophylaxis or treatment
* * Azithromycin and Clarithromycin have been considered reasonable alternatives by many clinicians, though their use has not formally been recommended by the CDC.

Immunizing children appropriately and on schedule is the best defense currently available to prevent pertussis. The new pertussis vaccine (acellular or DTaP) is effective and produces fewer side effects than whole cell DTP vaccines. A variety of DTaP vaccines are licensed for use in infants and children and have shown high levels of efficacy. As stated earlier, during this outbreak, we are recommending an accelerated immunization schedule for infants living in the affected community. This differs from the regular schedule in that it allows for the initiation of immunizations at six weeks of age (instead of two months), with the interval between immunizations reduced to four weeks (instead of eight).

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).

(Note: The pertussis cases in this article exceed the numbers on the back of this newsletter. This is a result of counting only confirmed cases in the Monthly Morbidity Summary.)

Rheumatic Fever

A presentation by Dr. Lloyd Tani, a pediatric cardiologist at Primary Children’s Medical Center (PCMC) was recently featured at the American Heart Association’s Scientific Sessions in Dallas, Texas. Dr. Tani provided an overview of research done on the 478 cases of rheumatic fever seen by physicians at PCMC since 1985. This study was prompted by a recent increase in the reported cases of rheumatic fever in Utah (for details see: May, 1998 Epidemiology Newsletter, Rheumatic Fever in Utah, 1998: (When a sore throat isn’t just a sore throat.....). Researchers are trying to gain an understanding of why the incidence is increasing, so that possible control measures can be identified. In cooperation with this research, the Bureau of Epidemiology routinely provides data on reported rheumatic fever cases. For the data to be as accurate as possible, it is important that all suspect and confirmed rheumatic fever cases are promptly reported to the Bureau of Epidemiology. For questions about reporting these cases, please contact the Bureau of Epidemiology at (801) 538-6191.

Utah Department of Health, Bureau of Epidemiology

Monthly Morbidity Summary - November 1998 - Provisional Data

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The Epidemiology Newsletter is published monthly by the Utah Department of Health, Division of Epidemiology and Laboratory Services, Bureau of Epidemiology, to disseminate epidemiologic information to the health care professional and the general public.

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

Approval 8000008: Appropriation 3705

Rod Betit, Executive Director Utah Department of Health
Charles Brokopp, Dr.P.H. Division of Epidemiology and Laboratory Services
Craig R Nichols, MPA, Editor, State Epidemiologist, Director Bureau of Epidemiology
Cristie Chesler, BA Managing Editor