Pertussis outbreak investigation in Saynt District, North eastern Ethiopia

Abstract

Background: Bordetella pertussis is a highly contagious, vaccine-preventable respiratory illness, transmitted by coughing. Globally there were an estimated 24.1 million cases and 160,700 deaths in children under five years with most in Africa. Little is known about pertussis burden in Ethiopia. On 09/12/2019, the Saynt Woreda was notified about 62 cases concerning for pertussis. Methods and materials: We used a probable case definition (≥2 weeks cough with vomiting, apnea, or inspiratory whoop) to identify pertussis cases through medical record review and active case search. Laboratory confirmation was not conducted for the study. We conducted an unmatched case control study with 71 cases and 142 asymptomatic neighbor controls using a structured questionnaire. We reviewed diphtheria, tetanus, pertussis (DTP3) administrative immunization coverage, determined vaccine history by parental interview/vaccination card. Results: We identified 546 cases with attack rate of [AR] = 3/1000 population, highest in 012 kebele (AR = 113/1000).All cases were from 012 kebele which is the most remote in the district, but no death recorded. There was no deployed health extension worker in the health post for two months before the outbreak. DPT3 coverage in the district was 86.1%. Most cases were 5–14 age group. Common clinical symptoms included whoop 70 (32.2%) and posttussive vomiting 65 (29.9%) while, only 6 (2.76%) patients had hernia. Overall 106 (48.85%) of respondents were vaccinated, 44 (20.28%) not vaccinated and the remaining vaccination status were not known. Being exposed to a possible case at school (OR = 13.3, 95% CI = 1.43–123.34, p-value = 0.0227) and living with the affected person with pertussis in the family (OR = 3.14, 95% CI = 1.38–7.15, p-value = 0.006) were contributing factors for pertussis outbreak while knowing way of prevention (OR = 0.26, 95% CI = 0.08–0.84, p-value = 0.02) is a protective factor to pertussis. Conclusion: The outbreak occurred in hard to reach villages/kebele of amhara saint woreda with a weak surveillance system and late detection was happen. Close contact with cases in the family and at school were contributing factors for pertusis outbreak. Active case search should be strengthening to facilitate early detection and isolation.