[The clinical and epidemiological characteristics of pertussis and antimicrobial resistance patterns of Bordetella pertussis in children in Anhui region in 2024].

Objective

To analyze the epidemiological and clinical characteristics of pertussis in children and the antimicrobial resistance pattern of Bordetella pertussis isolates in Anhui province in 2024.

Methods

Prospective observational study. The demographic information of 4 233 cases of pertussis confirmed by nucleic acid testing in Anhui Provincial Children's Hospital in 2024 and the clinical data of hospitalized cases were collected. The annual epidemic trend of pertussis in children, the clinical characteristics of hospitalized cases, and the vaccination status were analyzed. Bordetella pertussis isolates were recovered from nasopharyngeal swabs obtained from hospitalized children and their family caregivers during the outbreak period and antimicrobial susceptibility was tested.

Results

Among the 4 233 children, 2 330 were male and 1 903 were female. A total of 4 059 cases (95.9%) occurred from March to September, with the peak of the disease from April to July (3 364 cases (79.5%)).There were 4 075 cases (96.3%) aged 9 years and under, among which 718 cases (17.0%) were under 1 year old and 2 494 cases (58.9%) were aged 4 to 7 years. During the outbreak period, there were a total of 301 hospitalized children (7.1%), with an average age of 4.4 (2.8, 16.5) months. Among them, 61 cases (20.3%) received the full course of vaccination (4 doses), 64 cases (21.3%) received partial doses of the vaccine, and 176 cases (58.5%) were unvaccinated. Among the unvaccinated children, 79.6% (172/216) were under 1 year old, 8.7% (2/23) were between 1 and 3 years old, and 3.2% (2/62) were 3 years old or older. None of the 20 cases (6.6%) of severe pertussis received pertussis vaccine.Among the 301 hospitalized children, 298 cases (99.0%) presented with typical paroxysmal spasmodic cough, 94 cases (31.2%) had vomiting after coughing, 82 cases (27.2%) had whooping sounds, and 54 cases (17.9%) had cyanotic attacks. There were 228 cases (75.7%) complicated with pneumonia and 5 cases (1.7%) with pertussis encephalopathy. The infection rate among the accompanying family members who underwent screening was 77.1% (371/481). Based on the minimum inhibitory concentration testing of 186 Bordetella pertussis isolates, the minimum inhibitory concentration 90 of azithromycin and trimethoprim-sulfamethoxazole were >256.000 and 0.050 mg/L, respectively.

Conclusions

The peak of pertussis cases in Anhui region in 2024 occurred from April to July. Children aged ≤9 years were the major affected population. Infants and preschool children were most susceptible to pertussis. The intrafamily transmission rate of pertussis is high. Empirical use of macrolides for the treatment of pertussis is not recommended. Trimethoprim-sulfamethoxazole can be used as the preferred antibiotic for pertussis in children aged 2 months and above.