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Prolonged new cough in housemates linked to pertussis among infants
Pertussis affliction among infants shared a strong association with a prolonged cough in close household contacts, mostly among mothers, fathers and siblings, according to recent findings.
“Identifying infants’ transmission sources has challenged investigators. Frequently cited source studies were not designed to assess hypotheses including possible transmission by community contacts or persons with atypical symptoms and could not identify pertussis sources for 40% to 50% of infants,” C. Robinette Curtis, MD, MPH, of the immunization services division at the National Center for Immunization and Respiratory Diseases, CDC, and colleagues wrote. “In a 2006-2013 pertussis surveillance case series of infants <1 year of age, source(s) were not identified for 737 (56%) of 1,306 cases. Prior publications describe possible factors for further study, including exposures among >1 household, younger mothers, mothers with ≥7 days’ cough duration or Hispanic ethnicity.”
To determine the risks associated with pertussis affliction among infants, the CDC conducted a prospective study including 115 pertussis-confirmed infants aged 4 months or younger from four health department jurisdictions in the U.S. Further, the researchers matched two control infants to each case infant by age and either birth institution or residential area. All infants (n = 345) and their contacts aged 11 years or older underwent serologic testing for immunoglobulin G (IgG), and the CDC considered measurements of 94 units/mL or more pertussis toxin IgG enzyme-linked immunosorbent assay as seropositive.
Additionally, the CDC conducted structured interviews with the caregivers on whether respiratory symptoms or new cough was present within the household and prolonged (≥5 days) cough was present among household and visitor contacts.
Among all infants, there were 4,396 contacts during the study period. Eighty-three (72%) of the case patients had one or more contacts with prolonged new cough in their households; the most frequent contacts included siblings (34%), mother (28%) and father (12%). Further, 24 of these infants (29%) had a 20.1-fold (95% CI, 6.48-62.7) greater risk for pertussis from a visitor contact with a prolonged new cough compared with control infants.
Moreover, infants whose mothers had prolonged new cough had a 43.8-fold (95% CI, 6.45-298) risk for pertussis.
“In our study preceding national Tdap recommendations, U.S. infants ≤4 months of age during 2002-2005 whose mother had prolonged new cough (≥5 days) had 43.8-fold greater odds for pertussis; infants exposed to ≥1 nonmother contact with prolonged new cough in primary or secondary households had 20.1-fold greater odds for pertussis,” Curtis and colleagues wrote. “In contrast with studies that failed to identify sources for [about] 40% to 56% of infant cases, our data indicate that 72% of case-patients had identifiable possible pertussis transmission sources with ≥1 primary or secondary household contact having a prolonged (≥5 days) new cough.” – by Kate Sherrer
Disclosure: This study was funded by the National Vaccine Program Office and the CDC. The researchers report no relevant financial disclosures.
