Determining the Provincial and National Burden of Influenza-Associated Severe Acute Respiratory Illness in South Africa Using a Rapid Assessment Methodology

Local disease burden data are necessary to set national influenza vaccination policy. In 2010 the population of South Africa was 50 million and the HIV prevalence was 11%. We used a previously developed methodology to determine severe influenza burden in South Africa.
Hospitalized severe acute respiratory illness (SARI) incidence was calculated, stratified by HIV status, for four age groups using data from population-based surveillance in one site situated in Gauteng Province for 2009–2011. These rates were adjusted for each of the remaining 8 provinces based on their prevalence of risk factors for pneumonia and healthcare-seeking behavior. We estimated non-hospitalized influenza-associated SARI from healthcare utilization surveys at two sites and used the percent of SARI cases positive for influenza from sentinel surveillance to derive the influenza-associated SARI rate. We applied rates of hospitalized and non-hospitalized influenza-associated SARI to census data to calculate the national number of cases. The percent of SARI cases that tested positive for influenza ranged from 7–17% depending on age group, year, province and HIV status. In 2010, there were an estimated 21,555 total severe influenza cases in HIV-uninfected individuals and 13,876 in HIV-infected individuals. In 2011, there were an estimated 29,892 total severe influenza cases in HIV-uninfected individuals and 17,289 in HIV-infected individuals. The incidence of influenza-associated SARI was highest in children <5 years and was higher in HIV-infected than HIV-uninfected persons in all age groups. Influenza virus was associated with a substantial amount of severe disease, especially in young children and HIV-infected populations in South Africa.

制定国家流感疫苗接种政策，亟需本地疾病负担相关数据。2010年，南非总人口达5000万，人类免疫缺陷病毒（HIV）感染率为11%。本研究采用已成熟的研究方法，评估南非境内的重症流感疾病负担。
本研究以2009-2011年豪登省单个监测点的人群监测数据为基础，按HIV感染状态进行分层，划分4个年龄组，计算重症急性呼吸道疾病（Severe Acute Respiratory Illness, SARI）的住院发生率。基于其余8个省份的肺炎危险因素流行率与就医行为特征，对上述发生率进行校准调整。本研究通过两个监测点的医疗服务利用调查数据，估算非住院流感相关SARI发生率；同时结合哨点监测中流感检测阳性的SARI病例占比，推导流感关联SARI的整体发生率。将住院与非住院流感关联SARI的发生率代入人口普查数据，进而核算全国范围内的重症流感病例总数。
流感检测阳性的SARI病例占比介于7%~17%之间，具体数值因年龄组、年份、省份及HIV感染状态而异。2010年，估算HIV未感染者中重症流感总病例数为21555例，HIV感染者中为13876例；2011年，HIV未感染者中重症流感总病例数估算为29892例，HIV感染者中为17289例。流感关联SARI的发生率在5岁以下儿童中最高，且所有年龄组中HIV感染者的发生率均高于HIV未感染者。流感病毒与大量重症疾病的发生密切相关，在南非低龄儿童与HIV感染人群中尤为突出。