Varicella Outbreak at a Boarding School, Chikomba District, Mashonaland East Province, Zimbabwe, 2019

Background: Varicella is a contagious illness, caused by varicella zoster virus (VZV). It is transmitted via the respiratory route and through contact with the infected person. Fourteen cases of varicella from a boarding school in Chikomba District, Zimbabwe were reported on 14 February 2019. We investigated the outbreak to determine its scope, identify risk factors for transmission and recommend evidence-based control measures. Methods: A 1:2 unmatched case-control study was conducted. A case was a form one student at a boarding school in Chikomba District who developed acute onset of diffuse maculopapulovesicular rash without other apparent cause from 22 January 2019 to 24 February 2019. A control was a form one student at the same boarding school who did not develop the signs and symptoms of varicella during the same period. The diagnosis was based on clinical signs and symptoms. An interviewer-administered questionnaire was used to collect data. Epi info 7TM was used to calculate frequencies, odds ratios and perform logistic regression to control for confounding variables. Results: We recruited 31 cases and 62 controls. Independent risk factors for contracting varicella were classmate contact [AOR 24; (95% CI 4.4 - 83), p < 0.01], dormitory contact [AOR 14; (95% CI 2.7 - 75), p < 0.01] and previous history of varicella like illness [AOR 0.08; (95% CI 0.02 - 0.30), p < 0.01]. Only 35% (11/31) of cases and the majority 58 % (36/62) of controls, knew at least three signs and symptoms of varicella (p = 0.04). All cases were reported to the health facility within two days of onset of illness but were not managed according to guidelines. Conclusion: A perfect setting for the spread of infection was available in the form of students in a naive community living in close proximity both at class and at dormitories, which lead to the rapid transmission of the virus. Screening and isolation of the infected students controlled the outbreak.