The B. pertussis organism is most likely to be isolated during catarrhal stage or during the first 2 weeks of the paroxysmal cough stage. A nasopharyngeal specimen should be obtained before antibiotic therapy begins and submitted for a B. pertussis specific PCR test. Please refer to the VPDCP Patient Referrals to Public Health Centers for NP Pertussis PCR Testing protocol for guidance on obtaining a nasopharyngeal (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 and other direct antigen tests can yield rapid results but are often unreliable and should not be accepted for laboratory confirmation. Serologic tests are not recommended for the diagnosis of pertussis.

The Health District should begin investigation of pertussis cases within 1 working day of notification via IRIS.

Assigned investigator should collect the following elements:

1. Cough onset date, cough duration (<14 days or 14+ days), clinical history, complications. If the investigation begins less than 14 days after the patient’s cough onset, wait to do final interview at least 14 days after cough onset.
2. Laboratory reports.
3. Immunization status of patient*: Check CAIR for date(s) of administration, type of vaccine, vaccine manufacturer(s), lot number(s), and reason for non-vaccination if un- or under-vaccinated. If the patient is not in CAIR but patient reports being vaccinated, attempt to retrieve immunization records from the patient, their parents (if patient is a minor), or their provider.
   *Note: Not all immunization information may be available for every patient.
4. For infants <12 months of age: Determine hospital of birth, whether birthing parent received Tdap during the pregnancy, and if patient is hospitalized, the infant’s highest white blood cell (WBC) counts along with percent lymphocytes and test date for this infection.
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. See Contact Definition for what constitutes contact with a case. Consult with Vaccine Preventable Disease Control (VPDC) if there are any questions about the identification of new/presumptive cases.
7. If case is hospitalized, obtain hospital discharge summary. If unable to retrieve, contact VPDC investigators at VPDC@ph.lacounty.gov; they can assist in requesting medical records as needed.

All cases should be excluded from in-person activities including school or work for 21 days after cough onset, or until they have completed 5 days of appropriate antibiotic therapy, whichever happens first (see Table 2: Recommended Treatment and Postexposure Prophylaxis, by Age Group).

Separate index case from infants and other high-risk individuals until the case has completed 5 days of antibiotic therapy.

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

Antibiotic therapy is indicated before results are received if the clinical history is strongly suggestive of pertussis or the patient is at high risk of severe or complicated disease, such as an infant. A 5-day course of azithromycin is the appropriate first-line choice for treatment and for post-exposure prophylaxis. Please see Table 2: Recommended Treatment and Postexposure Prophylaxis, by Age Group for dosing and other treatment options.

Those who are considered high-risk for severe disease are:

• All asymptomatic household contacts, regardless of age or vaccination status.
• Infants <1 year old, especially those who have not yet received any doses of DTaP.
• Persons in their third trimester of pregnancy.
• Caregivers and household contacts of infants.
• All those attending or working in a childcare setting.
• Any other asymptomatic contacts with pre-existing conditions that may be worsened by pertussis, such as chronic lung disease or severe asthma.
• If a non-household contact has an uncertain level of exposure, PEP should be given if the contact is at high risk of severe disease or will have close contact with those at high risk of severe disease (e.g., young infant, pregnant person, person who works with infants or pregnant persons). PEP should be offered within 21 days of exposure to these contacts.
• The initiation of antibiotic prophylaxis for contacts who were exposed to a pertussis case more than 3 weeks ago has limited benefit and should not be routinely done unless the contacts are at high risk for developing severe disease (eg infants) or they are routinely exposed to high-risk persons (e.g., healthcare workers). In these instances, PEP can be given for up to 6 weeks after exposure.

Unvaccinated and under-vaccinated contacts should be offered DTaP or Tdap to bring them up to date per the American Academy of Pediatrics Catch-Up Immunization Schedule. Vaccination will not prevent disease from previous exposures but can protect patients from future exposures. Pertussis-containing vaccines and PEP can be administered at the same time.

1. All asymptomatic close contacts should be notified of exposure using the Exposure Notification for Individuals Exposed to Pertussis (available in English or Spanish).
2. All close contacts should passively monitor themselves for symptoms for 21 days after last contact with case during infectious period.
3. Symptomatic contacts should be excluded from school/daycare or other congregate settings, pending physician evaluation for pertussis with PCR testing.

Once VPDC confirms an outbreak, the following steps should be initiated in coordination with CFS, ACDC, and the school/school-based facility involved. Note that some of these steps may occur simultaneously.

1. VPDC creates outbreak record in IRIS and assigns to appropriate primary public health nurse (PHN). VPDC links all new identified cases after verifying epi-linkage with CFS and/or school representative(s).
2. VPDC notifies ACDC to add outbreak to weekly OB Log and provides weekly updates until outbreak is closed.
3. CFS identifies School Point(s) of Contact and sends Multi-Case Notification Letter to the School Point(s) of Contact, who then sends it to school staff and parents of school attendees (or directly to school attendees if in a college/university setting).
4. Within 3 business days of outbreak being confirmed, VPDC, CFS, and School Point(s) of Contact meet to review the outbreak investigation.
5. Within 2 business days of initial meeting, School Point(s) of Contact identifies all confirmed and probable cases and contacts and communicates that information to CFS.
6. CFS adds this information to CMaP within 1 business day of receipt.
7. CFS identifies all high-risk contacts (see High-Risk Close Contacts and Post-Exposure Prophylaxis (PEP)).
8. CFS provides case count updates (see below)*: After the initial coordination meeting between VPDC, CFS, and School Point(s) of Contact, CFS should enter all counts into CMaP event notes and update in CMaP event notes at least weekly. These counts should include:
   • Total number of confirmed cases
   • Total number of probable cases
   • All exposure sites and total number of exposed asymptomatic contacts from each site
   • Total number of high-risk and household contacts
   • Total number of high-risk contacts who have received PEP

*Note: All cases, household contacts, and high-risk contacts should be individually identified for each outbreak (see High-Risk Close Contacts and Post-Exposure Prophylaxis (PEP)). Low-risk asymptomatic contacts do not need to be individually identified for school outbreaks.

Classroom and other school-related contacts to the pertussis case (e.g., 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 Pertussis NP 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 an infectious pertussis case, or until they have completed 5 days of an appropriate antibiotic regimen, whichever happens first.

Asymptomatic close contacts for whom antibiotic post-exposure prophylaxis (PEP) is recommended may remain in school while completing PEP. If such asymptomatic persons decline PEP, they should still passively monitor themselves for signs and symptoms of pertussis. If they become symptomatic, they should be managed as symptomatic school contacts.

Once VPDC confirms an outbreak, the following steps should be initiated in coordination with CFS, ACDC, and the daycare facility involved. Note that some of these steps may occur simultaneously.

1. VPDC creates outbreak record in IRIS and assigns to appropriate primary PHN. VPDC links all new identified cases after verifying epi-linkage with CFS and/or school representative(s).
2. VPDC notifies ACDC to add outbreak to weekly OB Log and provides weekly updates until outbreak is closed.
3. CFS identifies Daycare Point(s) of Contact.
4. VPDC, CFS, and Daycare Point(s) of Contact meet to review the outbreak investigation.
5. CFS sends Multi-Case Notification Letter to the Daycare Point(s) of Contact, who then sends it to daycare staff and parents of daycare attendees.
6. Within 2 business days of outbreak being confirmed, Daycare Point(s) of Contact identifies all confirmed and probable cases and contacts and sends line list* to CFS.
7. CFS sends all line lists* to VPDC within 1 business day of receipt.
8. CFS identifies all high-risk contacts (see High-Risk Close Contacts and Post-Exposure Prophylaxis (PEP)).
   • CFS offers PEP to high-risk contacts as soon as they are identified.
   • Because daycare settings are “closed” settings like family/home settings, all asymptomatic daycare center contacts to a pertussis case should be offered antibiotic PEP. However, an asymptomatic daycare center contact who declines prophylaxis should not be excluded from daycare.
9. CFS provides case count updates (see below)*: After the initial coordination meeting between VPDC, CFS, and Daycare Point(s) of Contact, CFS should enter all counts into CMaP event notes and update in CMaP event notes at least weekly. These counts should include:
   • Total number of confirmed cases
   • Total number of probable cases
   • All exposure sites and total number of exposed asymptomatic contacts from each site
   • Total number of high-risk and household contacts
   • Total number of high-risk contacts who have received PEP

*Note: Line lists are required for all cases, household contacts, and high-risk contacts (see High-Risk Close Contacts and Post-Exposure Prophylaxis (PEP)). Asymptomatic contacts do not need to be listed unless daycare is an infant daycare or has more than 5% of unvaccinated attendees.

Once VPDC confirms an outbreak, the following steps should be initiated in coordination with the healthcare facility involved. Note that some of these steps may occur simultaneously.

1. VPDC creates outbreak record in IRIS and assigns to appropriate VPDC investigator. VPDC links all new identified cases after verifying epi-linkage with Healthcare Facility representative(s).
2. VPDC notifies ACDC to add outbreak to weekly OB Log and provides weekly updates until outbreak is closed.
3. VPDC identifies Healthcare Facility Infection Prevention and Control (IPC) representative(s) and/or other Point(s) of Contact.
4. VPDC meets with IPC and/or other Point(s) of Contact to review the outbreak investigation.
5. Within 1 business day of outbreak being confirmed, IPC representative(s) and/or other Point(s) of Contact identifies all confirmed and probable cases and contacts and sends line list to VPDC.
6. IPC representative(s) and/or Point(s) of Contact identifies all high-risk contacts (see High-Risk Close Contacts and Post-Exposure Prophylaxis (PEP)).
   1. PEP is recommended for all healthcare facility staff who have direct face-to-face contact with an infectious pertussis case and are likely to expose patients at risk of severe pertussis.
   2. Patients who have shared a room or other confined space with an infectious pertussis case for a prolonged period of time (≥1 hour) or who have had direct face-to-face contact with an infectious pertussis case should receive antibiotic prophylaxis to interrupt further transmission.
   3. Brief or casual waiting-room exposures generally do not warrant PEP unless the exposed individual is at high-risk for severe disease (e.g., infants < 1 year old, pregnant persons in their third trimester, or those with chronic medical conditions).
   4. Facilities should assess each situation based on duration, proximity, and ventilation of the shared space when determining who meets criteria for “shared airspace exposure”.
7. Exposed patients and staff should be cohorted (i.e., exposed staff should only work with other exposed staff and exposed or sick patients) if possible. New admissions to the ward of under/unvaccinated patients, or of any patients less than 1 year of age, should be avoided until all exposed patients and staff have been on antibiotic PEP for at least 5 days.
   
   In outpatient or ambulatory settings where cohorting is not possible and HCWs decline PEP, universal masking of exposed staff is recommended for 21 days after last exposure or until 5 days after starting antibiotic therapy, whichever comes first.
   
   Facilities should maintain a line list of all exposed staff, verify immunization status, encourage prompt PEP initiation, and monitor for cough or respiratory illness during the 21-day surveillance period.

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 for 21 days since their date of last exposure 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 an infectious pertussis case or until they have completed 5 days of an appropriate antibiotic regimen, whichever happens first.
• Because unvaccinated or under-vaccinated children are at higher risk for severe disease if they get pertussis, it is reasonable to offer PEP to this group.
• However, if they decline PEP and are asymptomatic, they should not be routinely excluded from school.

Refer to the posted exposure notification template letters for school settings (available in English or Spanish). Consult with VPDC for notification letters in other settings with school-aged children.