# Clinical characteristics analysis of pertussis and Mycoplasma pneumoniae infection in children

## TL;DR

This study compares the clinical features of pertussis and Mycoplasma pneumoniae infections in children to help doctors distinguish between the two.

## Contribution

The study identifies distinct demographic, seasonal, and clinical patterns between pertussis and Mycoplasma pneumoniae infections in children.

## Key findings

- Pertussis-only cases were more common in boys and occurred mainly in spring and winter.
- MP-only cases were more frequent in younger children and peaked in summer and autumn.
- Dual-positive cases showed unique patterns, including higher fever and different co-detected pathogens.

## Abstract

To analyze the clinical differences between pertussis and/or Mycoplasma pneumoniae (MP) infections in children and provide insights for clinical differential diagnosis.

We retrospectively reviewed children with respiratory symptoms who attended Shandong University Children’s Hospital (Jinan, China) from 2019 to 2024 and underwent simultaneous testing for pertussis and MP. Patients were categorized as pertussis-only, MP-only, or dual-positive, and differences in demographics, seasonality, manifestations, hematologic indices, and co-detected pathogens were analyzed.

A total of 7184 children were included: 2,982 pertussis-only, 3,166 MP-only, and 1,036 dual-positive. Significant differences were observed in sex (χ² = 30.964), age (χ² = 393.010), and season (χ² = 436.070) (all p < 0.001). Pertussis-only cases were more common in boys, during spring and winter, and in patients aged 6 years to <12 years. MP-only cases clustered in ages 2 to <6 and 6 to <12 years, with peaks in summer and autumn. Dual-positive cases were slightly more frequent in girls, clustered in the 6 to <12-year-old group, and occurred more often in spring and summer. Fever (χ² = 442.36, p < 0.001) was more frequent in the MP-only and dual-positive groups, whereas gastrointestinal symptoms (χ² = 30.00, p < 0.001), cyanosis (χ² = 12.91, p = 0.002), spasmodic cough (χ² = 212.07, p < 0.001), and cockcrow-like echo (χ² = 77.38, p < 0.001) were more common in the pertussis-only group. Lung crackles (χ² = 52.44, p < 0.001) and multilobar involvement (χ² = 28.08, p < 0.001) were predominantly observed in the MP-only group. The duration of cough before diagnosis was shorter in the MP-only group than in both the pertussis-only and dual-positive groups (H = 371.49, p < 0.001). Lymphocyte counts (H = 178.03) were the highest in the pertussis-only group, and neutrophil counts (H = 119.45) and C-reactive protein (H = 369.80) were the highest in the MP-only group (all p<0.001). Among the 7184 children, 1,224 (15.65%) had codetection of other pathogens, with human rhinovirus, Haemophilus influenzae, and Streptococcus pneumoniae most common. The MP-only group was more often accompanied with influenza A/B (χ² = 16.688, p < 0.001) and Legionella pneumophila (χ² = 12.715, p = 0.002); pertussis-only, Streptococcus pneumoniae (χ² = 11.872, p = 0.003); dual-positive, Klebsiella pneumoniae (χ² = 7.284, p = 0.009).

Pertussis and MP infections in children show distinct demographic, seasonal, clinical, and laboratory patterns. Recognition of these epidemiologic and clinical signatures supports early differentiation at the bedside and the use of multiplex PCR combined with specific laboratory markers to enable more targeted clinical management.