Pertussis

Infectious Agent

Fastidious gram-negative coccobacillus Bordetella pertussis .

Transmission

Person-to-person transmission via aerosolized respiratory droplets or by direct contact with respiratory secretions.

Epidemiology

Pertussis is endemic worldwide, even in areas with high vaccination rates. In recent years, pertussis has resurged in a number of countries with successful vaccination programs, especially countries that have transitioned from whole-cell pertussis vaccine formulations to acellular pertussis preparations, including the United States. In 2012, >48,000 cases of pertussis were reported nationally, the largest number in the United States since 1955. Disease rates are highest among young children in countries where vaccination coverage is low, which is primarily in the developing world. In developed countries, the reported incidence of pertussis is highest among infants too young to be vaccinated.

Immunity from 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. US travelers are not at increased risk for disease specifically because of international travel, but they are at risk if they come in close contact with infected people. Infants, especially those who are 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 disease, mild upper respiratory tract symptoms begin 7–10 days (range, 6–21 days) after exposure, followed by a cough that becomes paroxysmal. Coughing paroxysms can vary in frequency and are often followed by vomiting. Fever is absent or minimal. The clinical case definition for pertussis includes cough for ≥2 weeks with paroxysms, whoop, or posttussive vomiting.

Disease in infants aged <6 months can be atypical, with a short catarrhal stage, gagging, gasping, or apnea as early manifestations. Among infants aged <2 months, the case-fatality ratio is approximately 1%. Recently immunized children who develop disease may have mild cough illness; older children and adults may have prolonged cough with or without paroxysms. The cough gradually wanes over several weeks to months.

Diagnosis

Factors such as prior vaccination status, stage of disease, antibiotic use, specimen collection and transport conditions, and use of nonstandardized tests may affect the sensitivity, specificity, and interpretation of available diagnostic tests for B. pertussis . CDC guidelines for the laboratory confirmation of pertussis cases include culture and PCR (when the above clinical case definition is met); serology and direct fluorescent antibody tests are not confirmatory tests included in the current case definition for reporting purposes. Pertussis is a nationally notifiable disease.

Treatment

Macrolide antibiotics (azithromycin, clarithromycin, and erythromycin) are recommended to treat pertussis in people aged ≥1 month; for infants aged <1 month, azithromycin is the preferred antibiotic. Antimicrobial therapy with a macrolide antibiotic administered <3 weeks after cough onset can limit transmission to others. Postexposure prophylaxis is recommended for all household contacts of cases and for people at high risk of developing severe disease (such as infants and women in the third trimester of pregnancy) or those 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.

Prevention

Vaccine

Travelers should be up-to-date with pertussis vaccinations before departure. Multiple pertussis vaccines are available in the United States for infants and children, and 2 vaccines are available for adolescents and adults. A complete listing of licensed vaccines can be found at www.fda.gov/BiologicsBloodVaccines/Vaccines/ApprovedProducts/ucm093833.htm.

Infants and 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 4–6 years. An accelerated schedule of doses may be used to complete the DTaP series.

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 additional doses of tetanus and diphtheria toxoid-containing vaccines are needed, then they should be vaccinated according to catch-up guidance, with Tdap preferred as the first dose (www.cdc.gov/vaccines/schedules/hcp/imz/catchup.html).

Adolescents and Adults

Adolescents aged 11–18 years who have completed the recommended childhood DTwP/DTaP vaccination series and who have not previously received Tdap and 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. To provide pertussis protection before travel, Tdap can be given regardless of the interval from the last Td, except to people for whom pertussis vaccination is contraindicated or for people who have previously received Tdap. Adolescents and adults who have never been immunized against pertussis, tetanus, or diphtheria; who have incomplete immunization; or whose immunity is uncertain should follow the catch-up schedule established for Td/Tdap.

Pregnant Women

Women should have a dose of Tdap during each pregnancy, irrespective of her history of receiving Tdap. Although Tdap may 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.

CDC website: www.cdc.gov/pertussis

Bibliography

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Authors

Tami H. Skoff, Jennifer L. Liang