I Have Questions About Pertussis
How common is pertussis?
Over 20,000 cases of pertussis are reported each year (and about 10 deaths) in the United States (1,200 in Colorado ). This is felt to be a gross under estimate, and some experts estimate the actual number to be about one million in the US per year.
What is the classic clinical picture?
An incubation period of 5-7 days (range 4-21) is followed by a catarrhal stage lasting 7-14 days, and then the classic paroxysmal stage, with whoops and post-tussive emesis, lasting 1-6 weeks. The convalescent stage can last weeks to months, and exacerbations with other URIs/irritants (like cigarette smoke!) can be seen for at least a year.
What about atypical presentations?
In partially immune children, symptoms can be very mild and look like a typical URI. Many adults are diagnosed with “atypical pneumonia” without further testing. In emergency room studies, adults presenting with a cough of > 2 weeks had a 25% chance of having pertussis. Another special case is the neonate, who may present with apnea, seizures, encephalopathy or sepsis. A recent family history of paroxysmal cough or atypical pneumonia can be a clue in these cases, as most neonates catch pertussis from a household member.
What is the differential diagnosis?
Adenovirus (though coisolation not uncommon), parainfluenza, mycoplasma and chlamydia can all mimic pertussis. Bordatella parapertussis, which does not make functional pertussis toxin, can still cause pertussis like symptoms. In the immunocompromised, B. holmesii and B. bronchiseptica are uncommon causes of disease. Generally, B. bronchiseptica, which causes kennel cough in dogs, is not considered contagious to humans.
What is the best test?
Nasal wash for PCR. Our test will pick up Bordatella pertussis, the classic agent of Whooping Cough, and B. holmesii. It does not pick up B. parapertussis. PCR will remain positive in 90% for 4 and 60% for 7 days after treatment started. Nasal swabs for PCR are not as sensitive as nasal wash, and will not be accepted by our laboratory. The classic leukocytosis is only present in ~35%, but is a risk factor for severe disease.
How is test obtained, when is it run, and can I do it in my office?
Child can be sent for a nursing visit to the TCH ED for nasal wash, or it can be done in the office setting and sent in a sterile container to the TCH micro lab. The PCR is run daily, Monday through Friday, at 6:30am with results by 5pm . Instructions for obtaining a specimen can be obtained from the micro lab.
Is there ever a role for culture?
Culture takes about three weeks and requires special media. There may be a role for culture in a “relapsed” patient to document a medication failure (as PCR may still be positive though the bacteria is dead), and there is a role in special cases if you are looking for B. parapertussis or B. bronchiseptica in an immunosuppressed patient.
How contagious is pertussis?
The attack rate in a susceptible household member is at least 80%. In a person immunized in the last three years it is ~20%, and in a person immunized >12 years previous it is back up to >80%. Lest you think wild type disease provides fabulous immunity, rate is >50% after 15 years.
Who should get prophylaxis?
All household contacts should receive prophylaxis, regardless of immunization status. Vaccinations should also be updated. In addition, all “close contacts” should be prophylaxed. The TCH definition of “close contact” is: no droplet precautions used and direct face-to-face contact (within 3 feet) of a contagious patient or direct contact with the secretions of the patient. For daycare, these definitions also apply, and state health should be involved.
Which medications should be used?
Medications are the same for prophylaxis and treatment. This is from the Colorado Department of Public Health and Environment.
What about IHPS?
Erythromycin is a motilin agonist and an increase in hypertrophic pyloric stenosis, as well as other GI symptoms, has been observed in infants on erythromycin. Other macrolides also are motilin agonists, but not to the same degree as erythromycin, thus these agents are now recommended in that age group.
Who should get vaccinated?
The early childhood schedule calls for vaccination at 2, 4, 6, 15-18 and 4- 6 years. If exposure occurs, vaccination should be updated. Vaccination is now also recommended for adolescents aged 11-18. Boostrix is licensed for individuals 10 to 18 years, while Adacel is licensed for 11-64 years. Parents and other caretakers of infants may also be interested in the vaccine.
Last revised January 2006
