Data on the burden and risk groups for influenza-associated mortality from Africa are limited.
We aimed to estimate the incidence and risk-factors for in-hospital influenza-associated
severe acute respiratory illness (SARI) deaths.
Hospitalised patients with SARI were enrolled prospectively in four provinces of South Africa
from 2009–2013. Using polymerase chain reaction, respiratory samples were tested for ten
respiratory viruses and blood for pneumococcal DNA. The incidence of influenza-associated
SARI deaths was estimated at one urban hospital with a defined catchment population.
We enrolled 1376 patients with influenza-associated SARI and 3% (41 of 1358 with available
outcome data) died. In patients with available HIV-status, the case-fatality proportion
(CFP) was higher in HIV-infected (5%, 22/419) than HIV-uninfected individuals (2%, 13/620;
p = 0.006). CFPs varied by age group, and generally increased with increasing age amongst
individuals >5 years (p<0.001). On multivariable analysis, factors associated with death
were age-group 45–64 years (odds ratio (OR) 4.0, 95% confidence interval (CI) 1.01–16.3)
and 65 years (OR 6.5, 95%CI 1.2–34.3) compared to 1–4 year age-group who had the lowest
CFP, HIV-infection (OR 2.9, 95%CI 1.1–7.8), underlying medical conditions other than
HIV (OR 2.9, 95%CI 1.2–7.3) and pneumococcal co-infection (OR 4.1, 95%CI 1.5–11.2).
The estimated incidence of influenza-associated SARI deaths per 100,000 population was
highest in children <1 year (20.1, 95%CI 12.1–31.3) and adults aged 45–64 years (10.4,
95%CI 8.4–12.9). Adjusting for age, the rate of death was 20-fold (95%CI 15.0–27.8) higher
in HIV-infected individuals than HIV-uninfected individuals.
Influenza causes substantial mortality in urban South Africa, particularly in infants aged <1
year and HIV-infected individuals. More widespread access to antiretroviral treatment and
influenza vaccination may reduce this burden.