Clinical characteristics and risk factors for severe pertussis in infants aged less than 3 months.

BACKGROUND: Pertussis is a globally prevalent infectious disease caused by Bordetella pertussis. Although extensive research has examined pertussis in children, studies specifically focusing on infants aged less than 3 months remain limited. The aim of this study was to analyze the clinical characteristics of pertussis and the risk factors associated with severe pertussis in infants aged less than 3 months. METHODS: Clinical data from infants aged less than 3 months who were hospitalized with pertussis were retrospectively analyzed. Multivariate logistic regression analysis was conducted to determine risk factors for severe pertussis. RESULTS: This study included 205 infants aged <3 months with pertussis who were hospitalized at a provincial‑level tertiary referral center for pediatric infectious diseases in Anhui, China, between July 2021 and August 2025. The median age at disease onset was 59.0 [interquartile range (IQR), 40.5-73.0] days. Among 205 infants, the incidence of severe disease was 13.2% (27 cases). Compared with the non-severe group, the severe group demonstrated statistically significant differences in the presence of cyanotic episodes, whooping cough, fever, maximum white blood cell (WBC) count >30×109/L, and concurrent pulmonary consolidation (χ2=20.523, 5.52, 8.376, 35.194, and 21.446; all P<0.05). Multivariate logistic regression analysis indicated that fever [odds ratio (OR) =6.874, 95% confidence interval (CI): 2.155-21.931], whooping cough (OR =0.155, 95% CI: 0.032-0.764), cyanotic episodes (OR =18.82, 95% CI: 4.013-88.252), maximum WBC count >30×109/L (OR =15.755, 95% CI: 1.650-150.437), and pulmonary consolidation (OR =7.772, 95% CI: 1.376-43.908) were independently associated with severe pertussis. CONCLUSIONS: In infants aged less than 3 months with pertussis, the incidence of severe disease is 13.2% in this cohort. Fever, cyanotic episodes, a maximum WBC count >30×109/L, and pulmonary consolidation are independently associated with an increased risk of severe pertussis, whereas whooping cough is associated with a lower risk of severe disease.