CLINICAL CASE DEFINITION:
In the absence of a more likely diagnosis, a cough illness lasting ≥2 weeks with at least one of the following:

• Paroxysms of coughing; or
• Inspiratory "whoop"; or
• Post-tussive vomiting; or
• Apnea (with or without cyanosis)

LABORATORY CRITERIA FOR DIAGNOSIS:

• Isolation of B. pertussis from a clinical specimen; OR
• Positive polymerase chain reaction (PCR) for B. pertussis

EPIDEMIOLOGIC LINKAGE:
Contact with a laboratory-confirmed case of pertussis.

CONFIRMED
An acute cough illness of any duration with

• Isolation of B. pertussis from a clinical specimen; OR
• Polymerase chain reaction (PCR) positive for B. pertussis

PROBABLE

• In the absence of a more likely diagnosis, illness meeting the clinical criteria; OR
• Illness with cough of any duration, with
  • At least one of the following signs or symptoms:
    • Paroxysms of coughing; or
    • Inspiratory whoop; or
    • Post-tussive vomiting; or
    • Apnea (with or without cyanosis); AND
  • Contact with a laboratory confirmed case (epidemiologic linkage)       

There is no longer a suspect case category.

Health District should begin investigation of pertussis cases within one working day of notification via IRIS.

Assigned investigator should collect the following elements:

1. Onset and duration of cough, clinical history, complications. Wait to do final interview at least 14 days after cough onset.
2. Laboratory reports.
3. Immunization status of patient: date(s) of administration, type of vaccine, vaccine manufacturer(s), lot number(s), reason for non-vaccination.
4. For infants <12 months of age: determine hospital of birth, whether or not mother received Tdap during the pregnancy, and record highest WBC counts along with percent lymphocytes and test date.
5. Exposure to people with cough before illness onset.
6. Clinical and immunization status of household and other contacts. Complete a case report form for every contact that has a cough of any duration with at least one of the following: paroxysms, inspiratory whoop, or post-tussive vomiting. Consult with Vaccine Preventable Disease Control (VPDC) if there are any questions about the identification of new/presumptive cases.
7. Additional data for hospitalized patients require obtaining hospital discharge summaries.

All cases should be excluded from in-person activities including school or work for 21 days after cough onset, or until they have completed a full course of an appropriate antibiotic regimen (see Treatment & Antibiotic Prophylaxis below). If possible, separate index case from infants and other high-risk individuals until the case has completed full course of antibiotics.

A case admitted to a hospital ward before diagnosis or effective treatment should be kept in respiratory isolation for at least 5 days after the start of a course of appropriate antibiotic therapy.

Organism is most likely to be isolated during catarrhal stage and first 1-2 weeks of paroxysmal cough stage. A nasopharyngeal specimen should be obtained as soon as possible before antibiotic therapy begins and submitted for bacterial culture. Please refer to the VPDCP Patient Referrals to Public Health Centers for NP Pertussis PCR Testing protocol for guidance on obtaining a NP specimen. The PCR test is available commercially and can be used for lab confirmation in patients meeting the clinical criteria for pertussis. Fluorescent antibody (FA) tests as well as other direct antigen tests can yield rapid results but are often unreliable and should not be accepted for laboratory confirmation. Serological tests are not recommended.

Viral serologic test to exclude adenoviral illness may be considered. See Figure 1 for Specimen Collection Tubes.

See “Treatment & Antibiotic Prophylaxis” section under “Contact and Outbreak Management” for treatment guidance.

Unvaccinated and under-vaccinated contacts should be offered vaccines to bring them up to date per the CDC catch up schedule. Vaccination will not prevent disease from previous exposures but can protect patients from future exposures.

The recommended antibiotic prophylaxis and treatment regimens (which are the same) are listed below. Please be aware that current CDC guidelines recommend the exclusive use of azithromycin in infants under one month of age due to fewer adverse events compared to erythromycin. This is an “off-label” use of azithromycin.

Classroom (not daycare) and other school-related contacts to the pertussis case (i.e., band, sports teams) who develop signs and symptoms of pertussis should be referred to a health care provider for evaluation and may require an alternative diagnosis or a negative PCR to return to the classroom. If assessed to have pertussis, they should be excluded from school for 21 days after their last exposure to a communicable pertussis case, or until they have completed an appropriate antibiotic regimen.

Asymptomatic close contacts for whom antibiotic post-exposure prophylaxis (PEP) is recommended may remain in school while completing PEP. If such asymptomatic persons refuse PEP, they should be monitored for signs and symptoms of pertussis. If they become symptomatic, they should be handled as symptomatic school contacts as described above.

Based on recommendations from both the California Department of Public Health and the Centers for Disease Control and Prevention, asymptomatic close contacts that are unvaccinated or under-vaccinated against pertussis will not be routinely excluded from school merely because of the pertussis exposure. Such persons will be monitored for pertussis symptoms and referred for clinical evaluation and antibiotic treatment as appropriate. If such persons are assessed to have pertussis, they will be excluded from school for 21 days after their last exposure to a communicable pertussis case or until they have completed an appropriate antibiotic regimen. Because unvaccinated or under-vaccinated children have been shown to be at risk for severe disease if they get pertussis, as compared to fully vaccinated children, it is reasonable to offer asymptomatic unvaccinated or under-vaccinated children one course of PEP. However, if they refuse PEP and are asymptomatic, they should NOT be routinely excluded from school.

Refer to the posted exposure notification template letters for school settings. Consult with Vaccine Preventable Disease Control Program (VPDC) for notification letters in other settings with school-aged children.

Because daycare settings are “closed settings” similar to family/home settings, all asymptomatic daycare center contacts to a pertussis case should be offered antibiotic PEP. However, an asymptomatic daycare center contact who refuses prophylaxis should not be excluded from daycare.

Hospital or SNF staff with close (face-to-face or direct) personal contact with a communicable pertussis case and patients who have shared a room with a communicable pertussis case should receive antibiotic prophylaxis to interrupt further transmission. These patients and staff should also be cohorted in (i.e., restricted to) the involved ward and there should be no new admissions to the ward of inadequately immunized patients or of any patients less than 1 year of age, until all exposed patients and staff members have been on antibiotic PEP for at least 5 days.