Epidemiology of Severe Acute Respiratory Illness (SARI) among adults and children aged ≥5 years in a high HIV-prevalence setting, 2009-2012

Objective: There are few published studies describing severe acute respiratory illness (SARI) epidemiology amongst older children and adults from high HIV-prevalence settings. We aimed to describe SARI epidemiology amongst individuals aged ≥5 years in South Africa. Methods: We conducted prospective surveillance for individuals with SARI from 2009-2012. Using polymerase chain reaction, respiratory samples were tested for ten viruses, and blood for pneumococcal DNA. Cumulative annual SARI incidence was estimated at one site with population denominators. Findings: We enrolled 7193 individuals, 9% (621/7067) tested positive for influenza and 9%(600/6519) for pneumococcus. HIV-prevalence was 74% (4663/6334). Among HIV-infected individuals with available data, 41% of 2629 were receiving antiretroviral therapy (ART). The annual SARI hospitalisation incidence ranged from 325-617/100,000 population. HIV-infected individuals experienced a 13-19 times greater SARI incidence than HIV-uninfected individuals (p<0.001). On multivariable analysis, compared to HIV-uninfected individuals, HIV-infected individuals were more likely to be receiving tuberculosis treatment (odds ratio (OR):1.7; 95%CI:1.1-2.7), have pneumococcal infection (OR 2.4; 95%CI:1.7-3.3) be hospitalised for >7 days rather than <2 days (OR1.7; 95%CI:1.2-2.2) and had a higher case-fatality ratio (8% vs 5%;OR1.7; 95%CI:1.2-2.3), but were less likely to be infected with influenza (OR 0.6; 95%CI:0.5-0.8). On multivariable analysis, independent risk indicators associated with death included HIV infection (OR 1.8;95%CI:1.3-2.4), increasing age-group, receiving mechanical ventilation (OR 6.5; 95%CI:1.3-32.0) and supplemental-oxygen therapy (OR 2.6; 95%CI:2.1-3.2). Conclusion: The burden of hospitalized SARI amongst individuals aged ≥5 years is high in South Africa. HIV-infected individuals are the most important risk group for SARI hospitalization and mortality in this setting.