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

Abstract

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.

The national burden of influenza‐associated severe acute respiratory illness hospitalization in Zambia, 2011‐2014

“…In Step 1, we estimated the SARI hospitalizations rates in Lusaka Province (considered to be the base province in our estimation approach). In Step 2, we estimated the SARI hospitalizations rates for the other provinces from the base province using a previously described methodology 14, 15. In Step 3, we estimated the influenza‐associated SARI hospitalizations rates using available virological surveillance data for influenza.…”

“…Thereafter, we obtained the SARI hospitalization rates for the UTH by dividing the total number of SARI hospitalizations at the UTH (data source 2) by the estimated service population. We used the UTH SARI hospitalization rates as a proxy for Lusaka Province as previously described 14, 15…”

“…Risk factors included HIV infection, exposure to indoor air pollution, crowding, malnutrition, low birthweight, and non‐exclusive breastfeeding 14, 15. The last three were only included for children aged <5 years.…”

“…The relative risk of SARI associated with each risk factor was determined from the published literature 14, 15, 16, 17, 18. In addition, we adjusted the provincial rates by the proportion of ARI cases seeking care in the given province to the proportion of ARI cases seeking care in the base province using data from the DHS (data source 4) as previously described (Step 2.b) 14, 15. The healthcare‐seeking behavior among ARI cases was used as a proxy for SARI cases.…”

“…We estimated the provincial rates of influenza‐associated SARI hospitalization by multiplying the estimated provincial SARI hospitalization rates (obtained in Step 1 and 2) by the influenza virus detected rate obtained from influenza sentinel surveillance implemented among inpatients with SARI (data source 3) 14, 15…”