Outbreak of influenza A in a boarding school in South Africa, 2016

• Published in: The Pan African medical journal Vol. 33; no. 42; p. 42
• Main Authors: Kleynhans, Jackie, Treurnicht, Florette Kathleen, Cohen, Cheryl, Vedan, Theesan, Seleka, Mpho, Maki, Lwando, von Gottberg, Anne, McCarthy, Kerrigan, Ramkrishna, Wayne, McMorrow, Meredith, Walaza, Sibongile
• Format: Journal Article
• Language: English
• Published: Uganda African Field Epidemiology Network 2019; The African Field Epidemiology Network; The Pan African Medical Journal
• Subjects: Adolescent; boarding school; Child; Cohort analysis; Cohort Studies; cohort study; Cross-Sectional Studies; cross-sectional study; Disease Outbreaks; Female; Humans; Immunization; influenza; Influenza A Virus, H3N2 Subtype - isolation & purification; Influenza Vaccines - administration & dosage; Influenza, Human - epidemiology; Influenza, Human - virology; Male; Medical records; outbreak; Retrospective Studies; Risk Factors; Schools; South Africa - epidemiology; Students; Vaccines; Young Adult; South Africa; United States > US; influenza; outbreak; cross-sectional study; Boarding school; cohort study
• DOI: 10.11604/pamj.2019.33.42.16666
• ISSN: 1937-8688

We investigated an outbreak of influenza-like illness (ILI) at a boarding school in Eastern Cape Province, South Africa. We aimed to confirm the etiological agent, estimate attack rates and identify risk factors for illness. We conducted a retrospective cohort study including senior school boarders (n=308). Students with ILI (cough and fever) were identified through school medical records. We also conducted a questionnaire-based cross-sectional study among senior students including boarders (n=107) and day students (n=45). We collected respiratory specimens for respiratory pathogen testing by real-time polymerase chain reaction from a subset of symptomatic students. We calculated attack rates of medically attended ILI (medILI) and identified factors associated with medILI using logistic regression. We calculated seasonal influenza vaccine effectiveness (VE) against medILI. Influenza A (H3N2) virus was detected in 61% (23/38) of specimens. Attack rate for medILI was 13% among boarders (39/308) in the cohort study and 20% in both day students (9/45) and boarders (21/107) in the cross-sectional study. Playing squash was associated with medILI (aOR 5.35, 95% confidence interval [95% CI]: 1.68-17.07). Of the boarders, 19% (57/308) were vaccinated before the outbreak. The adjusted VE against medILI was 18% (aOR 0.82, 95% CI 0.38-1.78). The outbreak led to cancellation of several events and the need for academic remedial sessions. We confirmed an influenza A (H3N2) virus outbreak with a high attack rate. The outbreak affected academic and sports activities. Participation in sports and social gatherings while experiencing ILI should be discouraged to reduce viral transmission and impact on school activities.