INTRODUCTION
Despite the use of interventions such as antimicrobial drugs and vaccination against leading pneumonia-causing pathogens, acute respiratory infections (ARI) remain a major cause of death globally, especially among children aged <5 years [11World Health Organisation. Global Health estimates 2016: Deaths by cause, age, sex, by country, Region, 2000-2016. 2018 . Available at: www.who.int/news-room/fact-sheets/detail/the-top-10-causes-of-death. Accessed 29 January 2020]. In addition, mild and severe-non-fatal episodes of ARI are responsible for a substantial burden on the healthcare systems and the society, through illness, absenteeism, and associated costs.
The Pneumonia Etiology Research for Child Health (PERCH) study conducted in 7 low- and middle-income countries, including South Africa, estimated that respiratory viruses were responsible for 61% of severe pneumonia cases (compared to 27% due to bacteria) among HIV-uninfected children aged <5 years [22Pneumonia Etiology Research for Child Health (PERCH) Study Group. Causes of severe pneumonia requiring hospital admission in children without HIV infection from Africa and Asia: the PERCH multi-country case-control study. Lancet. 2019 ;394(10200):757-779. doi: 10.1016/S0140-6736(19)30721-4.]. This suggests that, as bacterial etiologies decline due to vaccination, respiratory viral causes may gain greater prominence [2]. Nonetheless, the relative contribution of respiratory viruses in individuals of all ages remains poorly understood.
HIV infection is associated with increased severity of ARI and higher case-fatality ratios, especially in older children and younger adults [33Cohen C, Walaza S, Moyes J, at al. Epidemiology of viral-associated acute lower respiratory tract infection among children <5 years of age in a high HIV prevalence setting, South Africa, 2009-2012. Pediatr Infect Dis J.2015 ;34(1):66-72. doi: 10.1097/INF.0000000000000478.,44Cohen C, Walaza S, Moyes J, et al. Epidemiology of severe acute respiratory illness (SARI) among adults and children aged ≥5 years in a high HIV-prevalence setting, 2009-2012. PLoS One. 2015 ;10(2):e0117716. doi: 10.1371/journal.pone.0117716.]. In South Africa, a country with an HIV prevalence of 12.7% in the general population and 23.5% in individuals aged 25-44 years in 2016 [55Statistics South Africa. Mid-Year Population Estimates. Pretoria, South Africa: Statistics South Africa. 2016 . Available at: https://www.statssa.gov.za/publications/P0302/P03022016.pdf. Accessed 29 January 2020.], pneumonia and influenza were the leading causes of death among children aged <5 years and the 3rd and 5th causes of death among older individuals, resulting in 19,638 deaths annually in the same year [66Statistics South Africa. Mortality and causes of death in South Africa. 2016 . Available at: https://www.statssa.gov.za/publications/P03093/P030932016.pdf. Accessed 29 January 2020.]. Whereas the etiology of hospitalized severe pneumonia among HIV-uninfected children aged <5 years has been described in South Africa [2], the overall burden on the healthcare system and society of mild and severe respiratory illness overall and associated with respiratory viruses across age groups has not been quantified. Quantifying this burden may assist policy makers with allocation of resources and prioritization of interventions.
In this study, we sought to assess the mean annual national burden of medically and non-medically attended influenza-like illness (ILI) and severe respiratory illness (SRI) overall and associated with nine respiratory viruses in different age groups in South Africa during 2013-2015.