Influenza- and respiratory syncytial virus-associated adult mortality in Soweto

Background: Influenza and respiratory syncytial virus (RSV) infections cause seasonal excess mortality and hospitalisation in adults, particularly the elderly, in high-income countries. Little information exists on the impact of these infections on African adults. Objectives: To estimate influenza- and RSV -related adult mortality, stratified by age, and hospitalisation in Soweto, South Africa. Study design: A retrospective hospital-based study in Soweto from 1997-1999 to estimate influenza- and RSV -related excess all-cause deaths and hospitalisation using a rate-difference method. It was based on influenza seasons of varying severity provided by surveillance data. Results: Influenza seasons were significantly associated with excess mortality in adults across all 3 years, except for 18-64 year olds in 1998. Excess mortality was highest in those ≥65 years of age, 82.8 /100 000 population in the mild 1997 season and 220.9 / 100 000 in the severe 1998 season. Influenza significantly increased adult medical hospitalisation in the severe 1998 season alone. RSV did not significantly affect mortality or hospitalisation. Conclusions: Influenza-related mortality was substantial and disproportionately affected the elderly. Influenza vaccination for the elderly needs consideration. The RSV -related burden was not significantly increased but merits observation over a longer period.