Abstract: Objective　To explore the risk factors of death in severe pertussis in infants. Methods　The clinical data of pertussis in infants including 25 dead cases (death group) and 80 severe cases (survival group) admitted from January 1, 2015 to October 31, 2019 were analyzed retrospectively. Results　In the death group, there were 5 males (20%), median onset age was 77 days and 20 patients (80%) had not received pertussis vaccine. The survival group had 47 males (58.8%, median onset age was 83 days and 63 patients (78.8%) had not been vaccinated. Compared with the survival group, the death group had fewer males, lower incidence of spasmodic cough, higher incidence of pulmonary consolidation (or atelectasis), more significantly increased peripheral white blood cell count (WBC), higher incidence of pulmonary hypertension, and lower proportion of gamma globulin usage, and the differences were statistically significant (P<0.05). Multivariate logistic regression analysis found that males and gamma globulin usage were the protective factors for the death in severe pertussis (OR=0.03, 0.03), the highest WBC and pulmonary hypertension were the risk factors for death (OR= 1.10, 13.31), and the death rate of children with spastic cough was lower (OR= 0.02). The optimal cut-off value of the highest WBC for predicting death is 55.37 × 109/L, and the area under curve (AUC) was 0.83 (95% CI: 0.73~0.93, P<0.001). Conclusions　Unvaccinated, hyperleucaemia and pulmonary hypertension significantly increased the mortality of severe pertussis in infants. The use of gamma globulin and early blood exchange may improve the prognosis of hyperleukaemia. Use hormones with caution.

Key words: pertussis;　death;　risk factor;　leukocytosis;　infant