Jackie Kleynhans
Centre for Respiratory Diseases and Meningitis (CRDM), National Institute for Communicable Diseases (NICD) of the National Health Laboratory Service (NHLS), Johannesburg, South Africa;South African Field Epidemiology Training Programme (SA-FETP), NICD of the NHLS, Johannesburg, South Africa
Florette Kathleen Treurnicht
South African Field Epidemiology Training Programme (SA-FETP), NICD of the NHLS, Johannesburg, South Africa
Cheryl Cohen
Centre for Respiratory Diseases and Meningitis (CRDM), National Institute for Communicable Diseases (NICD) of the National Health Laboratory Service (NHLS), Johannesburg, South Africa
Theesan Vedan
South African Field Epidemiology Training Programme (SA-FETP), NICD of the NHLS, Johannesburg, South Africa
Mpho Seleka
Centre for Respiratory Diseases and Meningitis (CRDM), National Institute for Communicable Diseases (NICD) of the National Health Laboratory Service (NHLS), Johannesburg, South Africa
Lwando Maki
Division of Public Health, Surveillance and Response (DPHSR), NICD of the NHLS, Johannesburg, South Africa
Anne von Gottberg
Centre for Respiratory Diseases and Meningitis (CRDM), National Institute for Communicable Diseases (NICD) of the National Health Laboratory Service (NHLS), Johannesburg, South Africa; School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
Kerrigan McCarthy
School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa;Division of Public Health, Surveillance and Response (DPHSR), NICD of the NHLS, Johannesburg, South Africa
Wayne Ramkrishna
South African National Department of Health (NDoH), Pretoria, South Africa
Meredith McMorrow
Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America;U.S. Centers for Disease Control and Prevention, Pretoria, South Africa
Sibongile Walaza
Centre for Respiratory Diseases and Meningitis (CRDM), National Institute for Communicable Diseases (NICD) of the National Health Laboratory Service (NHLS), Johannesburg, South Africa; School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
Abstract
Introduction: 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. Methods: 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. Results: 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. Conclusion: 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.
