Risk Factors for Influenza-Associated Severe Acute Respiratory Illness Hospitalization in South Africa, 2012–2015

Abstract

Background.Data on risk factors for influenza-associated hospitalizations in low- and middle-income countries are limited.Methods.We conducted active syndromic surveillance for hospitalized severe acute respiratory illness (SARI) and outpatient influenza-like illness (ILI) in 2 provinces of South Africa during 2012–2015. We compared the characteristics of influenza-positive patients with SARI to those with ILI to identify factors associated with severe disease requiring hospitalization, using unconditional logistic regression.Results.During the study period, influenza virus was detected in 5.9% (110 of 1861) and 15.8% (577 of 3652) of SARI and ILI cases, respectively. On multivariable analysis factors significantly associated with increased risk of influenza-associated SARI hospitalization were as follows: younger and older age (<6 months [adjusted odds ratio {aOR}, 37.6], 6–11 months [aOR, 31.9], 12–23 months [aOR, 22.1], 24–59 months [aOR, 7.1], and ≥65 years [aOR, 40.7] compared with 5–24 years of age), underlying medical conditions (aOR, 4.5), human immunodeficiency virus infection (aOR, 4.3), and Streptococcus pneumoniae colonization density ≥1000 deoxyribonucleic acid copies/mL (aOR, 4.8). Underlying medical conditions in children aged <5 years included asthma (aOR, 22.7), malnutrition (aOR, 2.4), and prematurity (aOR, 4.8); in persons aged ≥5 years, conditions included asthma (aOR, 3.6), diabetes (aOR, 7.1), chronic lung diseases (aOR, 10.7), chronic heart diseases (aOR, 9.6), and obesity (aOR, 21.3). Mine workers (aOR, 13.8) and pregnant women (aOR, 12.5) were also at increased risk for influenza-associated hospitalization.Conclusions.The risk groups identified in this study may benefit most from annual influenza immunization, and children <6 months of age may be protected through vaccination of their mothers during pregnancy.

Burden and epidemiology of influenza‐ and respiratory syncytial virus‐associated severe acute respiratory illness hospitalization in Madagascar, 2011‐2016

“…Among individuals aged ≥5 years, the Madagascar estimates (11.6 per 100 000 population) were generally consistent with the estimates obtained from similar studies conducted in Africa: South Africa (22.1 per 100 000 population), Kenya (30.0 per 100 000 population), Rwanda (11 per 100 000 population), and Zambia (13 per 100 000 population) . Underlying medical conditions including HIV infection are known risk factors for influenza‐associated severe illness . Differences in the prevalence of such conditions in these settings may explain some of the observed variation in the influenza‐associated SARI hospitalization rates in this age group.…”

The effects of the attributable fraction and the duration of symptoms on burden estimates of influenza‐associated respiratory illnesses in a high HIV prevalence setting, South Africa, 2013‐2015

“…We observed a U‐shaped trend of the magnitude of the influenza‐associated SARI and SCRI hospitalization rates across age groups. Young children and older individuals are known to be at increased risk of influenza‐associated severe illness . In our study, the highest rates of influenza‐associated SARI hospitalization were among children aged <1 year, whereas the highest rates of influenza‐associated SCRI hospitalization were among individuals aged ≥65 years.…”

“…HIV‐infected patients were at increased risk of influenza‐associated mild or severe illness compared to HIV‐uninfected patients. HIV infection has been reported to be associated with increased risk of influenza‐associated SARI hospitalization in other studies . The RR of HIV infection to illness among influenza‐positive patients with ILI or SCRI has not been described to our knowledge.…”

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

“…Our estimates of influenza‐associated SARI hospitalization in individuals aged ≥5 years are on the lower end, but overall similar to other estimates from Africa (22 per 100 000 population in South Africa 21 and 30 per 100 000 population in Kenya 20). Underlying medical conditions including HIV infection is known risk factors for influenza‐associated severe illness 21, 22, 23, 24. Differences in the prevalence of such conditions in different settings may explain some of the observed differences in the influenza‐associated SARI hospitalization rates in this age‐group.…”