Health Advisory

Pertussis Advisory

To:     Health Care Providers, Hospitals, Ambulatory Care Centers
From: Patsy Kelso, State Epidemiologist for Infectious Disease
Date:  November 15, 2011

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Recent Cases of Pertussis in Vermont
In the past two weeks, the Vermont Department of Health has received an increased number of reports of pertussis. Since mid-October, five cases have been confirmed: four laboratory-confirmed (three including positive culture and PCR, and one by PCR only), and one clinical case epidemiologically linked to a laboratory-confirmed case. Patients are from the following counties: Chittenden (3), Bennington (1), and Washington (1). Ages of these patients range from 5 months to 67 years. One adult older than 70 from Windham County was diagnosed with clinical pertussis, with no testing done. Twelve suspected cases reported since November 1 remain under investigation, along with clusters in two schools. In all, pertussis illness has been confirmed or reported since mid-October from five counties: Chittenden, Bennington, Windham, Addison and Washington.

Laboratory Testing
Testing not only provides diagnostic information for the patient, but supports public health interventions to decrease disease transmission in the community. Culture in combination with PCR (polymerase chain reaction assays) is the preferred option for testing. PCR tests for pertussis are more rapid and sensitive than culture, which is 100 percent specific but has low sensitivity (12% to 60%). See information below regarding best practices to avoid false-positive, false-negative, or inconclusive PCR results.

Protecting Infants
Infants are best protected by providing Tdap booster doses to household contacts while the infant receives the first three doses of DTaP by age 6 months. Pertussis illness is most severe in infants. Many infants are infected by family members or caregivers who have undiagnosed disease.

Actions Requested –

1. Report suspected cases to the Vermont Department of Health (802-863-7240 or 1-800-640-4374) to allow for timely public health interventions. Pertussis presents with mild upper respiratory symptoms and an irritating cough that gradually increases in severity to the classic symptoms of pertussis: paroxysmal coughing along with possible whooping, apnea, or post-tussive vomiting. In the youngest infants, atypical presentation is common. The cough may be minimal or absent and the primary symptom may be apnea.

2. Test for pertussis. Recommended best practices to avoid false-positive, false-negative, or inconclusive PCR results include collecting specimens within three weeks of cough onset, and before or as early as possible after starting antibiotics. PCR testing following antibiotic therapy can result in false-negative findings. False-positive or inconclusive results can occur when testing asymptomatic people, especially close contacts of cases. Specimens should be collected using a Copan or Dacron nasopharyngeal swab, and transported in Regan Lowe charcoal medium.

Because PCR is highly sensitive, adherence to good clinical practices is essential. If possible, prepare and administer vaccines in areas separate from pertussis specimen collection areas. Accidental transfer of the DNA from environmental surfaces to a clinical specimen can result in specimen contamination and false-positive or inconclusive results.

Testing for B. pertussis is available at the Vermont Department of Health Laboratory. Please request VDH Kit #5 for proper collection and transport materials. Culture testing (no charge) or culture/PCR testing ($36) can be requested. Culture results are available within seven days of receipt at the Health Department Laboratory, and PCR is performed on Mondays and Thursdays.

In an outbreak situation, or by special request, PCR testing may be performed on a day other than Monday or Thursday by calling Epidemiology at 802-863-7240.

3. Provide vaccination. Vaccination is the best protection against pertussis. Because immunity from childhood pertussis vaccination wanes over time, the adolescent/adult pertussis booster vaccine (Tdap) for adolescents and adults is essential to reduce the risk of contracting pertussis and can decrease severity of disease. Vaccinating adolescents and adults, especially family members or caregivers of infants and health care workers, can help prevent pertussis transmission to infants too young to be vaccinated.

One dose of Tdap vaccine is recommended for people 11 years and older. There is no minimal time interval between doses of Td and Tdap.

Specific indications for Tdap in those who are high-risk:

For providers participating in the Vermont VFC/VFA program, Adacel® is available for children age 10 to 18 years and Boostrix® is available for those 19 years and older. Contact the VDH Immunization program at 802-863-7240 for information about ordering vaccine.

Treatment
Early treatment of pertussis is very important. The earlier a person, especially an infant, starts on treatment the better, since treatment before coughing paroxysms occur may help to lessen symptoms. Clinicians should strongly consider treating prior to receiving test results if clinical history indicates pertussis or if the patient is at risk for severe or complicated disease (e.g., infants). The prompt initiation of prophylaxis to household and other close contacts of clinical cases is also important in order to avert secondary transmission. Dosages and duration of therapy are the same for treatment of cases and prophylaxis of contacts. Information on preferred treatment options is available through the following CDC website:

Exclusion
Because pertussis is a highly infectious disease, anyone who has clinical or lab-confirmed pertussis should be excluded from school, work, and group activities until five days of antibiotic therapy have been completed. Asymptomatic contacts who are receiving antibiotic prophylaxis do not need to restrict their activities.

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