Chapter 3Infectious Diseases Related To Travel

Tami H. Skoff, Cynthia G. Thomas

INFECTIOUS AGENT

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

MODE OF TRANSMISSION

Pertussis is spread by 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. From 2004 through 2008, the annual number of reported pertussis cases in the United States ranged from approximately 4,000 to 25,000. 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 unvaccinated infants and increases again among adolescents.

Immunity from childhood vaccination and natural disease wanes with time; therefore, adolescents and adults who have not received a 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.

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 may be frequent or relatively infrequent 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 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.

TREATMENT

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. The recommended agents and dosing regimens for prophylaxis are the same as for the treatment of pertussis.

PREVENTIVE MEASURES FOR TRAVELERS

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.

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 should receive a single dose of Tdap instead of Td for booster immunization against tetanus, diphtheria, and pertussis. Tdap vaccine, when indicated, should be administered to adolescents regardless of interval since the last dose of Td vaccine.

Adults aged 19–64 years who have not previously received Tdap should receive a single dose of Tdap to replace a single dose of Td for booster immunization against tetanus, diphtheria, and pertussis regardless of interval since their last tetanus toxoid-containing vaccine (such as Td). Adults aged ≥65 years who have or who anticipate having close contact with an infant aged <12 months and who have not previously received Tdap should receive a single dose of Tdap to protect against pertussis and reduce the likelihood of transmission; all other adults ≥65 years who have not previously received Tdap may be given a single dose of Tdap instead of Td.

Tdap can be given regardless of interval from the last Td to provide pertussis protection before travel, except to people for whom vaccination is contraindicated or for people who have been 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.

BIBLIOGRAPHY

1. American Academy of Pediatrics. Pertussis. In: Pickering LK, Baker CJ, Long SS, McMillan JA, editors. Red Book: 2006 report of the Committee on Infectious Diseases. 27th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2006. p. 498–520.
2. Broder KR, Cortese MM, Iskander JK, Kretsinger K, Slade BA, Brown KH, et al. Preventing tetanus, diphtheria, and pertussis among adolescents: use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccines. Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2006 Dec 15;55(RR-17):1–33.
3. CDC. Pertussis vaccination: use of acellular pertussis vaccines among infants and young children. Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 1997 Mar 28;46(RR-7):1–25.
4. CDC. Updated recommendations for use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccine from the Advisory Committee on Immunization Practices, 2010. MMWR Morb Mortal Wkly Rep. 2011 Jan 14;60(1):13–5.
5. Edwards KM, Decker MD. Pertussis vaccines. In: Plotkin SA, Orenstein WA, editors. Vaccines. 4th ed. Philadelphia: WB Saunders; 2004. p. 471–528.
6. Tiwari T, Murphy TV, Moran J. Recommended antimicrobial agents for the treatment and postexposure prophylaxis of pertussis: 2005 CDC Guidelines. MMWR Recomm Rep. 2005 Dec 9;54 (RR-14):1–16