Author(s): Tami Skoff, Anna Acosta

Infectious Agent

Pertussis is caused by Bordetella pertussis, a fastidious gram-negative coccobacillus.

Transmission

B. pertussis transmission occurs person-to-person via aerosolized respiratory droplets or by direct contact with respiratory secretions.

Epidemiology

Pertussis is endemic worldwide, even in areas with high vaccination rates. International travel, therefore, does not generally place US travelers at increased risk for infection, as compared to home. Travelers are, however, at increased risk if they come into close contact with infected people. Pertussis has resurged in many countries with successful vaccination programs, especially countries that have transitioned from whole-cell pertussis vaccine formulations to acellular pertussis preparations, including the United States. Although limited data are available on the global burden of pertussis, disease rates are presumed to be highest among young children in countries where vaccination coverage is low, primarily developing countries. In industrialized countries, reported pertussis incidence is highest among infants too young to be vaccinated.

Immunity conferred by childhood vaccination and natural disease wanes with time; therefore, adolescents and adults who have not received a tetanus-diphtheria-pertussis (Tdap) booster vaccination can become infected or reinfected with pertussis. Infants, especially those too young to be protected by a complete vaccination series, are at highest risk for severe illness and death from pertussis.

Clinical Presentation

In classic pertussis disease, mild upper respiratory tract symptoms typically begin 7–10 days (range 5–21 days) after exposure (catarrhal stage), after which a cough develops and becomes paroxysmal (paroxysmal stage). Coughing paroxysms can vary in frequency and often are followed by vomiting. Fever is absent or minimal. The coughing paroxysms gradually resolve into milder and less frequent coughing, but paroxysms can recur with subsequent respiratory infections (convalescent stage). The clinical case definition for pertussis includes cough for ≥2 weeks with paroxysms, whoop, post-tussive vomiting, or apnea with or without cyanosis.

Infants aged <6 months can have atypical disease, with a short catarrhal stage, gagging, gasping, or apnea as early manifestations. Among infants aged <2 months, the case-fatality ratio is ≈1%. The illness can be milder, and the characteristic paroxysmal cough and whoop might be absent, in children, adolescents, and adults who were previously vaccinated.

Diagnosis

Factors such as prior vaccination status, disease stage, antibiotic use, specimen collection and transport conditions, and use of nonstandardized tests can affect the sensitivity, specificity, and interpretation of available diagnostic tests for B. pertussis. Centers for Disease Control and Prevention (CDC) guidelines for laboratory confirmation of pertussis include culture and PCR when the above clinical case definition is met. Serology is not included as a confirmatory test in the current case definition for reporting purposes. Direct fluorescent antibody (DFA) testing is no longer recommended for diagnosing pertussis because of poor sensitivity and specificity. Testing for B. pertussis is widely available in commercial laboratories. Clinicians can consult Vaccine-Preventable Diseases Reference Centers for additional testing support if needed. Pertussis is a nationally notifiable disease.

Treatment

Clinicians can treat pertussis in people aged ≥1 month with a macrolide antibiotic (azithromycin, clarithromycin, or erythromycin); for infants aged <1 month, azithromycin is preferred. Antimicrobial drug therapy with a macrolide antibiotic administered <3 weeks after cough onset can limit transmission to others.

Prevention

Vaccine

Travelers should be up to date on pertussis vaccinations before departure. Multiple pertussis vaccines are available in the United States for infants and children; 2 vaccines are available for adolescents and adults. See complete listing of licensed vaccines.

Infants & Children

In the United States, all infants and children should receive 5 doses of acellular pertussis vaccine in combination with diphtheria and tetanus toxoids (DTaP) at ages 2, 4, 6, and 15–18 months, and at 4–6 years. Providers can use an accelerated schedule of doses to complete the DTaP series before travel, if needed.

Children aged 7–10 years who are not fully vaccinated against pertussis and for whom no contraindication to pertussis vaccine exists should receive a single dose of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine (Tdap) to provide protection against pertussis. If children need additional doses of tetanus and diphtheria toxoid–containing vaccines, administer them according to catch-up guidance, with Tdap preferred as the first dose.

Adolescents & Adults

Adolescents aged 11–18 years who have completed the recommended childhood DTaP vaccination series should receive a single dose of Tdap, preferably at age 11–12 years. Adults aged ≥19 years who have not previously received Tdap should receive a single dose of Tdap instead of tetanus and diphtheria toxoids (Td) vaccine for booster immunization against tetanus, diphtheria, and pertussis, regardless of the interval since their last tetanus or diphtheria toxoid–containing vaccine.

To ensure continued protection against tetanus and diphtheria, administer booster doses of either Td or Tdap every 10 years throughout a patient’s life. Follow the catch-up schedule for Td/Tdap for adolescents and adults who have never been immunized against pertussis, tetanus, or diphtheria; who have not completed an immunization series; or whose immunity is uncertain.

Pregnant People

Even if vaccinated previously, a person should receive a dose of Tdap with each pregnancy. Although Tdap can be given at any time during pregnancy, to maximize the maternal antibody response and passive antibody transfer to the infant, optimal timing for Tdap administration is at 27–36 weeks’ gestation, preferably during the earlier part of the period.

Postexposure Prophylaxis

Postexposure prophylaxis is recommended for all household contacts of cases and for people at high risk of developing severe disease (e.g., infants, people in the third trimester of their pregnancy, anyone who will have contact with a person at high risk of severe illness). The recommended agents and dosing regimens for prophylaxis are the same as for the treatment of pertussis.

CDC website: Pertussis