Person-to-person transmission via aerosolized respiratory droplets or by direct contact with respiratory secretions.
Pertussis is endemic worldwide, even in areas with high vaccination rates. From 2004 through 2010, the annual number of reported pertussis cases in the United States ranged from approximately 8,000 to >27,000. 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 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 too young to be protected by a complete vaccination series are at highest risk for severe pertussis that requires hospitalization.
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.
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 (DFA) tests are not confirmatory tests included in the case definition.
Macrolide antibiotics (azithromycin, clarithromycin, and erythromycin) are recommended for the treatment of 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 close contacts of cases and for people at high risk of developing severe disease (such as infants and those who will have contact with young infants). The recommended agents and dosing regimens for prophylaxis are the same as for the treatment of pertussis.
Complete vaccination of children aged <7 years with 5 doses of acellular pertussis vaccine in combination with diphtheria and tetanus toxoids (DTaP) is recommended; 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 Tdap to provide protection against pertussis. If additional doses of tetanus and diphtheria toxoid-containing vaccines are needed, then children aged 7–10 years should be vaccinated according to catch-up guidance, with Tdap preferred as the first dose. 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. Tdap vaccine, when indicated, should be administered to adolescents and adults regardless of interval since the last dose of Td vaccine.
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. Tdap can be substituted for any one of the Td doses in the series.
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