Controlling Spread of Pertussis

A. Identifying close contacts and high risk populations

Close Contact: While each situation should be evaluated separately and exposure defined based on information acquired through the investigation, close contacts are generally defined as persons who:

• Shared confined space in close proximity with a symptomatic case patient for greater than one hour;
• Had direct face-to-face contact for a period (not defined) with a symptomatic case while they were infectious; or
• Had direct contact with respiratory, oral, or nasal secretions from a symptomatic case-patient (e.g., an explosive cough or sneeze in the face, sharing food, sharing eating utensils during a meal, kissing, mouth-to-mouth resuscitation, or performing a medical exam including examination of the nose and throat).

High Risk Populations: The following groups are generally considered to be at high risk of developing severe illness:

• Infants <12 months and women in their third trimester of pregnancy -- severe and sometimes fatal pertussis-related complications occur in infants aged <12 months, especially among infants aged <4 months. Women in their third trimester of pregnancy may be a source of pertussis to their newborn infant.
• All persons with pre-existing health conditions that may be exacerbated by a pertussis infection (for example, but not limited to immunocompromised persons and patients with moderate to severe medically treated asthma).

B. Recommended Treatment Protocol

The symptoms of pertussis may be modified if treatment is begun early, during the catarrhal stage. If started later in the course of the illness, treatment will decrease the infectious period, but may not decrease the duration of cough or severity of disease. 

If symptomatic people are already beyond their infectious period, which ends 21 days after cough onset, treatment is generally not beneficial. However, for certain high-risk settings or individuals (such as pregnant women in their third trimester or infants less than 12 months), healthcare providers may consider extending the period for initiating treatment up to six weeks after symptoms start.

A specific class of antibiotics called macrolides is most effective against pertussis. The table below summarizes recommended oral antibiotics and dosages by age group.

(Recommended Antimicrobial Agents for the Treatment and Postexposure Prophylaxis of Pertussis, 2005 CDC Guidelines, available at: www.cdc.gov/mmwr/preview/mmwrhtml/rr5414a1.htm?s_cid=rr5414a1_e)

Trimethoprim sulfamethoxazole (TMP-SMZ) may be used as an alternative agent in patients aged =2 years who are allergic to macrolides, who cannot tolerate macrolides, or who are infected, rarely, with a macrolide-resistant strain of Bordetella pertussis.

• The recommended dose in children is trimethoprim 8 mg/kg/day, sulfamethoxazole 40 mg/kg/day in two divided doses for 14 days.
• For adults, the recommended dose is trimethoprim 320 mg/day, sulfamethoxazole 1600 mg/day in two divided doses for 14 days.

NOTE: Because of the risk of kernicterus, TMP-SMZ should not be given to pregnant women, nursing mothers, premature neonates, or infants <two months of age.

NOTE: Only limited data from small clinical trials are available that confirm the microbiologic effectiveness of macrolides in infants < six months of age with pertussis, who are more likely to be partially or  unimmunized and whose colonization is more likely to be prolonged compared with older, previously immunized individuals with pertussis.

• Nevertheless, considering theoretical rationale, in vitro effectiveness, safety and clinical data in older individuals with pertussis, and treatment adherence issues, the macrolides listed above may be used as a first line agent in infants 1 to 6 months of age.
• For infants <1 month of age, the risk of developing severe pertussis and life threatening complications outweighs the potential risk of infantile hypertrophic pyloric stenosis (IHPS) that is associated with macrolide use. All infants <1 month of age who receive any macrolide should be monitored for the development of IHPS and, as with other antibiotics with limited experience, for other serious adverse events.

C. Post Exposure Antimicrobial Prophylaxis Recommendations

The primary goal of post exposure antimicrobial prophylaxis is to prevent death and serious complications from pertussis in individuals at increased risk of severe disease. Appropriate administration of antimicrobial prophylaxis to asymptomatic contacts can prevent symptomatic infection.  

Prophylaxis is generally indicated when:

• The asymptomatic contact was exposed to the case during the case’s infectious period (<21 days after onset of cough in the case), and
• The asymptomatic contact’s last exposure to the infectious case occurred <21 days (one incubation period) ago. 

However, at their discretion, healthcare providers could consider prophylaxis of high-risk close contacts up to six weeks after exposure.

Prophylaxis is generally recommended for the following groups, regardless of their immunization status:

• All household contacts (within families, secondary attack rates have been demonstrated to be high, even when household contacts are current with immunizations),
• Close contacts at high risk of developing severe illness, or
• Close contacts who themselves have close contact with either infants <12 months, pregnant women in their third trimester, or individuals with pre-existing health conditions that may be exacerbated by a pertussis infection.
• All contacts in high risk settings that include infants <12 months or pregnant women in their third trimester (such as neonatal intensive care units, childcare settings, and maternity wards).

(See Section A. Identifying close contacts and high risk populations on page 5, for further clarification of “close contacts” and “high risk”)

A broader use of PEP may be recommended in rare situations.  Please contact your field epidemiologist or CADE for consultation or questions regarding these situations.

The recommended antibiotics and dosage by age group is identical for treatment and prophylaxis.  Therefore, refer to the table in Section 3.B Recommended Treatment Protocol on page 6 for the schedule.

Repeat Exposures

When continued transmission of pertussis is evident, multiple rounds of antibiotics are not recommended unless:

1. the close contact is determined to be at high risk, or
2. the close contact has close contact with persons at high risk.

(Section 3. A. Identifying close contacts and high risk populations)    

Rather than repeating a course of antibiotics, close contacts determined not to be at high risk and not to have close contact with persons at high risk, should be monitored for onset of signs and symptoms of pertussis for 21 days. 

If repeat prophylaxis is appropriate, the additional points should be considered: 

• If the repeat exposure occurred less than 5 days after completion of the initial course of azithromycin (5 day course), no additional prophylaxis is needed. 
• If the repeat exposure occurred more than 5 days after completion of the initial course of azithromycin or if a different prophylactic antibiotic (Clarithromycin, Erythromycin, or TMP-SMZ) was prescribed for the first exposure, another course of antibiotics should be prescribed. 

D. Isolation

Cases:

If the patient has already coughed for more than 21 days at the time of diagnosis, the individual is no longer contagious to others and isolation is not indicated.
Cases who have been coughing fewer than 21 days should stay home (this includes exclusion from social settings such as school, child care, work, church, and the mall) until they have completed the first five days of the full course of an appropriate antibiotic. During this time, they also should not have visitors.
Cases who refuse antibiotics should stay home (this includes exclusion from social settings such as school, child care, work, church, and the mall) through 21 days after cough onset.  During this time, they should not have visitors.
Asymptomatic contacts:

Prophylactic antibiotics are offered (to household contacts, close contacts at high risk of developing severe illness, and to close contacts who themselves have close contact with persons at high risk) to prevent others from becoming ill with pertussis or spreading the disease to those at high risk for severe disease.
Therefore, asymptomatic close contacts are not contagious and they do not need to be excluded from social settings.  They should be monitored for the development of symptoms.

Symptomatic contacts (Epi-link case):

Symptomatic contacts should be referred to a physician for treatment and testing if appropriate (See section 2.C. Laboratory Testing).

If symptomatic contacts have already coughed for 21 days at the time of diagnosis, the individual is no longer contagious to others and isolation is not indicated.

Symptomatic contacts, who have coughed fewer than 21 days, should be placed on antibiotics, isolated to home, and considered infectious until having completed the first five days of the full course of an appropriate antibiotic.

Symptomatic contacts who refuse antibiotics should stay home (this includes exclusion from social settings such as school, child care, work, church, and the mall) through 21 days after cough onset.  During this time, they should not have visitors.

If the physician defers antibiotics until diagnostic test results are available, the symptomatic contact should be excluded from social settings until results become available.  If results are negative, the individual may return immediately unless the clinician makes the diagnosis of pertussis on the basis of clinical and epidemiologic data. 

E. Vaccination and Preventive Measures

The focus of vaccination is the prevention of the spread of pertussis in general; therefore all contacts that are not up to-date with DTaP/DTP/Tdap should be brought up-to-date. 

For current recommendations for vaccination, visit the Iowa HHS Immunization and Tuberculosis web page.

The following points provide additional detail and clarification related to pertussis immunizations:

• Active immunization started after exposure will not protect against disease resulting from that exposure, but it is not contraindicated. It will decrease the risk for disease from future exposure.  The best protection is obtained by adhering to the recommended schedule. 
• Assess the immunization status of close contacts. Children who are unimmunized or under immunized should have immunization initiated, completing the series with minimum intervals.
• Children who have received their third dose of DTP/DTaP >six months before exposure should receive a fourth dose.
• Supplemental vaccination is not recommended for children who are up-to-date for age.
• While the use of an accelerated routine schedule of pertussis vaccination for infants (e.g., aged <two months at initial vaccination) during pertussis outbreaks is considered an acceptable outbreak control measure, it is usually not recommended because it would not match the schedule of other needed vaccinations.  DTaP vaccines are not licensed for use in infants less than six weeks of age. The impact of implementing an accelerated schedule is likely to be modest, but could result in some decrease in pertussis morbidity among infants between 14 weeks and six months of age.
• Pertussis vaccine does not protect against infection by B. parapertussis.
• Many experts recommend children (especially infants aged <12 months) who have had a history of pertussis disease complete the routine vaccination series for pertussis with DTaP.  This is because the duration of protection from pertussis disease is unknown and the diagnosis of pertussis can be difficult to confirm, especially if testing methods other than PCR are used.  At least one study found that infants (age<12 months) may have a suboptimal immune response following pertussis disease.

While routine vaccination is the best preventive measure against pertussis, good personal hygiene (which consists of proper hand hygiene, disposal of used tissues, etc.) is also important.

F. Managing Special Situations

While the basic principles of case investigation, treatment of cases, and close contact prophylaxis also apply to these settings, additional considerations are included below.

Schools and Preschools

(If preschool is part of larger childcare setting, see child care center section below.)

Pertussis outbreaks have occurred even with high vaccine coverage levels (persons with three or more doses of pertussis containing vaccine).  Often outbreaks are not limited to a single class or grade.  Attack rates vary by grade and school activities.  Transmission in school settings may include other children, the teacher in the classroom, or other social groups such as athletic teams or clubs.

Prophylaxis recommendations follow those outlined in Section 3. C. Post Exposure Antimicrobial Prophylaxis Recommendations. When identifying close contacts, it is important to determine if there are any patterns of interaction that would increase exposure time among a group (such as children living in the same neighborhood, riding the same bus, going to the same school, and participating in the same activities, etc.).

The following checklist should be used when investigating cases and outbreaks in school and preschool settings. Work with the school nurse and appropriate teachers to take the following actions:

1. Identify close contacts among students and staff who interact directly with the case.
2. Evaluate close contacts (students and staff) for cough illness.
3. Refer close contacts to their healthcare provider for appropriate treatment, isolation, or prophylaxis (see Section 3. B. Recommended Treatment Protocol, Section C. Post Exposure Antimicrobial Prophylaxis Recommendations, and Section 3.D. Isolation).  A School/Childcare Close Contact Letter Template is included in this chapter for distribution among close contacts; these may be issued on the stationery of the local public health agency or the affected institution.
4. Consider sending a general notification home with all students, acknowledging that there has been a case of pertussis in the school and encouraging parents to ensure their children are “up to date” on vaccine (in particular the adolescent booster) and to be aware of signs and symptoms and what to do if they occur. A School-wide / Childcare-wide General Notification Pertussis Letter Template is included in this chapter; these may be issued on the stationery of the local public health agency or the affected institution.
5. Request that all teachers in the school refer coughing students to the nurse’s office.
6. Maintain a pertussis surveillance log that includes a line listing for all symptomatic individuals with cough onset and duration, labs, antibiotic type and start and finish date, location (in schools, grade and home room), and other symptoms present. On a separate list, keep track of the close contacts, recording the names and locations of students and staff (classrooms, teams, etc.).  See school contact letter included in this chapter.

NOTE:  Close Contact letters that recommend consideration of prophylactic antibiotics given to minors should be accompanied by a phone or email to parents notifying them of the letter.  This follow-up could be performed by secretarial staff, for example, and does not have to be done by a health professional.  This additional phone or email communication is NOT necessary for the school-wide, general notification letter.

Childcare

Usually children in child care centers have extensive contact with each other and it can be difficult to distinguish individuals with or without significant exposure.

Exposures occurring in child care settings without children less than 12 months of age (no infants in the childcare center) should be managed in accordance with Section 3.C. Post Exposure Antimicrobial Prophylaxis Recommendations.

For cases occurring in child care settings with children less than 12 months of age (there are infants in the childcare center), the recommendations are based upon whether children are divided into multiple classrooms. 

• If there are multiple classrooms that do not intermingle, and:
  • The exposure occurs in a room with children less than 12 months of age, it is recommended that the case’s entire class and assigned staff be considered close contacts and they should all be advised to receive prophylaxis (because they are or have contact close contact with a child less than 12 months).
  • The exposure occurs in a room with children greater than 12 months of age, all children should be considered exposed and prophylaxis should be managed in accordance with Section 3.C. Post Exposure Antimicrobial Prophylaxis Recommendations on page 7.
    • In this situation, it would be appropriate to distribute the School/Childcare Close Contact Letter Template to all children and staff assigned to the same classroom as the case.
  • In both cases, the School-wide / Childcare-wide General Notification Pertussis Letter Template should be distributed to all children and staff in the facility (all classrooms).
• If the child care center is not divided into separate classes, it is recommended that the entire center and all staff be considered close contacts and receive prophylaxis (because they have contact close contact with a child less than 12 months). 
  • In this situation, the School/Childcare Close Contact Letter Template would be appropriate to distribute to all children/families and staff.

In home-based child care settings with at least one child less than 12 months of age, it is recommended that all children and all child care providers (including any members of the child care providers’ families who had any contact with the case during their infectious period) receive prophylaxis.

• In this situation, the School/Childcare Close Contact Letter Template would be appropriate to distribute to all children/families and staff.

Offices and other facilities

The basic principles of case and contact investigation, treatment of cases, and prophylaxis of close contacts apply (see Section 3. B. Recommended Treatment Protocol , Section C. Post Exposure Antimicrobial Prophylaxis Recommendations, and Section 3.D. Isolation).  A General Close Contact Letter Template for distribution among close contacts is included in this chapter; these may be issued on the stationery of the local public health agency or the affected facility.

Depending upon the situation and facility a general notification letter may also be appropriate. A General Pertussis Notification Letter Template is also included in the Forms and Fact Sheets tab; these may be issued on the stationery of the local public health agency or the affected facility.

NOTE:  Close Contact letters, which recommend prophylactic antibiotics according to the high risk criteria, that are given to minors should be accompanied by a phone or email to parents notifying them of the letter.  This follow-up could be performed by secretarial staff, for example, and does not have to be done by a health professional.  This additional phone or email communication is NOT necessary for the general notification letter.

Healthcare Facilities

In healthcare settings, surveillance should be initiated immediately after identification of a suspect case and continue through two incubation periods (42 days) after the date of cough onset in the last case. Healthcare provider’s pertussis vaccination should be up-to date. A single dose of Tdap is recommended for all health care personnel who have not previously received Tdap as an adult.

Regardless of their vaccination status, healthcare providers should use appropriate masks in the presence of a patient with cough illness to prevent exposures from occurring. 

• Healthcare workers exposed to a case who have appropriately followed Standard Precautions and Droplet Precautions (including wearing a mask) during close contact with the case, do not require prophylaxis.
• Recommendations for healthcare workers exposed to a case, who have not appropriately followed Standard Precautions and Droplet Precautions (did not wear a mask) during close contact with the case, are based upon the setting and patient populations they serve:
• Asymptomatic healthcare workers, who work with patients at risk for severe pertussis (see Section 3. A. Identifying close contacts and high risk populations ) should receive prophylaxis (see Section 3. C. Post Exposure Antimicrobial Prophylaxis Recommendations). Examples of these high risk settings would include neonatal intensive care units, cancer treatment units, and maternity wards.
• Other asymptomatic healthcare workers, who do not work with high risk patients, can be monitored for 21 days after exposure and prophylaxis is not required.  If the healthcare worker becomes symptomatic, they should be excluded immediately.
• When cases occur within healthcare facilities (i.e., a patient is hospitalized with pertussis):
  • Apply Droplet and Standard Precautions to all staff, patients, and families in close contact with the case.

In healthcare settings, “close contact” is defined as the following:

• having face-to-face contact, within three feet of the case; this includes conducting a medical examination, obtaining a nasopharyngeal swab, suctioning, intubating, performing bronchoscopy or similar procedure without appropriate PPE;
• conducting any procedure that induces coughing of the case, even if farther from the case than three feet without appropriate PPE;
• coming into mucosal contact with respiratory, oral, or nasal secretions of the case directly; and
• sharing a room with the case.

The basic principles of case and contact investigation, treatment of cases, and prophylaxis of close contacts apply (see Section 3. B. Recommended Treatment Protocol , Section C. Post Exposure Antimicrobial Prophylaxis Recommendations, and Section 3.D. Isolation).

Providers, department heads, infection prevention, employee health, and other relevant personnel/departments should be notified of the case.

Institutional Setting

In institutional settings (e.g. correctional facilities), prophylaxis recommendations may vary depending upon this situation.  Please contact your field epidemiologist or CADE for consultation or questions regarding these situations.

Iowa Dept. of Public Health, Reviewed 7/15