Tempia, StefanoWalaza, SibongileMoyes, JocelynCohen, Adam L.Von Mollendorf, ClaireMcMorrow, Meredith L.Mhlanga, SaronaTreurnicht, Florette K.Venter, MarietjiePretorius, Marthi A.Hellferscee, OrienkaWolter, NicoleVon Gottberg, AnneNguweneza, ArthemonMcAnerney, Johanna M.Dawood, HalimaVariava, EbrahimMadhi, Shabir A.Cohen, Cheryl2018-06-122018-06-122018-05Tempia, S., Walaza, S., Moyes, J. et al. 2018, 'The effects of the attributable fraction and the duration of symptoms on burden estimates of influenza-associated respiratory illnesses in a high HIV prevalence setting, South Africa, 2013-2015', Influenza and Other Respiratory Viruses, vol. 12, no. 3, pp. 360-373.1750-2640 (print)1750-2659 (online)10.1111/irv.12529http://hdl.handle.net/2263/65127BACKGROUND : The attributable fraction of influenza virus detection to illness (INF-AF) and the duration of symptoms as a surveillance inclusion criterion could potentially have substantial effects on influenza disease burden estimates. METHODS : We estimated rates of influenza-associated influenza-like illness (ILI) and severe acute (SARI-10) or chronic (SCRI-10) respiratory illness (using a symptom duration cutoff of ≤10 days) among HIV-infected and HIV-uninfected patients attending 3 hospitals and 2 affiliated clinics in South Africa during 2013-2015. We calculated the unadjusted and INF-AF- adjusted rates and relative risk (RR) due to HIV infection. Rates were expressed per 100 000 population. RESULTS : The estimated mean annual unadjusted rates of influenza-associated illness were 1467.7, 50.3, and 27.4 among patients with ILI, SARI-10, and SCRI-10, respectively. After adjusting for the INF-AF, the percent reduction in the estimated rates was 8.9% (rate: 1336.9), 11.0% (rate: 44.8), and 16.3% (rate: 22.9) among patients with ILI, SARI-10, and SCRI-10, respectively. HIV-infected compared to HIV-uninfected individuals experienced a 2.3 (95% CI: 2.2-2.4)- , 9.7 (95% CI: 8.0-11.8)- , and 10.0 (95% CI: 7.9-12.7)- fold increased risk of influenza-associated illness among patients with ILI, SARI-10, and SCRI-10, respectively. Overall 34% of the estimated influenza-associated hospitalizations had symptom duration of >10 days; 8% and 44% among individuals aged <5 and ≥5 years, respectively. CONCLUSION : The marginal differences between unadjusted and INF-AF- adjusted rates are unlikely to affect policies on prioritization of interventions. HIV-infected individuals experienced an increased risk of influenza-associated illness and may benefit more from annual influenza immunization. The use of a symptom duration cutoff of ≤10 days may underestimate influenza-associated disease burden, especially in older individuals.en© 2017 The Authors. Influenza and Other Respiratory Viruses Published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License.Attributable fractionInfluenzaRatesSevere respiratory illnessSymptom durationHuman immunodeficiency virus (HIV)South Africa (SA)SurveillanceHospitalizationMortalityInfectionInfluenza-like illness (ILI)Article