Epidemiologic characteristics of pertussis cases detected in Shanghai, 2017

ObjectiveTo understand the epidemiological characteristics of pertussis in Shanghai in 2017 and to provide evidence for the development of pertussis prevention and control measures.

MethodsThe incidence data of pertussis in Shanghai in 2017 were collected from national notifiable diseases registry system (NNDRS) and district CDCs in Shanghai for a descriptive analysis.

ResultsIn 2017, a total of 258 pertussis cases were reported by 6 sentinel hospitals in Shanghai. The incidence peak was during August-September. The cases in age groups ＜18 months and ≥20 years accounted for 50.00% and 41.47% respectively. The male to female ratio of the cases was 1∶1.28. The ratio of cases with local residence to cases without local residence was 1∶1.29. The cases were distributed in 75% of the districts in Shanghai. More than 50% cases aged 5 months - 14 years received at least 3 doses of pertussis-containing vaccines. The incidence rates of typical symptoms of vomiting, cyanosis or inspiratory stridor were all ＜30%. Among the close contacts with symptom of cough, the adults aged ≥20 years accounted for 71.88%. The positive rate of nasopharyngeal swab detection in PCR was 30.50%, while the positive rate of PT-IgG was 41.07%.

ConclusionThe sensitivity of pertussis surveillance in Shanghai was greatly improved in 2017 due to the efforts of sentinel hospitals. Less cases showed typical symptoms of pertussis, a high proportion of cases had vaccination history. It is suggested revise the case definition of probable case of pertussis and improve the diagnosis of pertussis.