Attributable Fraction of Influenza Virus Detection to Mild and Severe Respiratory Illnesses in HIV-Infected and HIV-Uninfected Patients, South Africa, 2012-2016.

The attributable fraction (AF) of influenza virus detection to illness has not been described for patients in different age groups or with different HIV infection statuses. We compared the age group-specific prevalence of influenza virus infection among patients with influenza-like illness (ILI) or severe acute or chronic respiratory illness (SARI and SCRI, respectively) with that among controls, stratified by HIV serostatus. The overall AF for influenza virus detection to illness was 92.6% for ILI, 87.4% for SARI, and 86.2% for SCRI. Among HIV-uninfected patients, the AF for all syndromes was highest among persons <1 and >65 years of age and lowest among persons 25-44 years of age; this trend was not observed among HIV-infected patients. Overall, influenza viruses when detected in patients with ILI, SARI, or SCRI are likely attributable to illness. This finding is particularly likely among children and the elderly irrespective of HIV serostatus and among HIV-infected persons irrespective of age.

Influenza and tuberculosis co-infection: A systematic review.

INTRODUCTION: There are limited data on risk of severe disease or outcomes in patients with influenza and pulmonary tuberculosis (PTB) co-infection compared to those with single infection. METHODS: We conducted a systematic review of published literature on the interaction of influenza viruses and PTB. Studies were eligible for inclusion if they presented data on prevalence, disease association, presentation or severity of laboratory-confirmed influenza among clinically diagnosed or laboratory-confirmed PTB cases. We searched eight databases from inception until December 2018. Summary characteristics of each study were extracted, and a narrative summary was presented. Cohort or case-control studies were assessed for potential bias using the Newcastle-Ottawa scale. RESULTS: We assessed 5154 abstracts, reviewed 146 manuscripts and included 19 studies fulfilling selection criteria (13 human and six animal). Of seven studies reporting on the possible effect of the underlying PTB disease in patients with influenza, three of four analytical studies reported no association with disease severity of influenza infection in those with PTB, whilst one study reported PTB as a risk factor for influenza-associated hospitalization. An association between influenza infection and PTB disease was found in three of five analytical studies; whereas the two other studies reported a high frequency of PTB disease progression and complications among patients with seasonal influenza co-infection. CONCLUSION: Human analytical studies of an association between co-infection and severe influenza- or PTB-associated disease or increased prevalence of influenza co-infection in individuals' hospitalized for PTB were not conclusive. Data are limited from large, high-quality, analytical epidemiological studies with laboratory-confirmed endpoints.

Health and economic burden of influenza-associated illness in South Africa, 2013-2015.

BACKGROUND: Economic burden estimates are essential to guide policy-making for influenza vaccination, especially in resource-limited settings. METHODS: We estimated the cost, absenteeism, and years of life lost (YLL) of medically and non-medically attended influenza-associated mild and severe respiratory, circulatory and non-respiratory/non-circulatory illness in South Africa during 2013-2015 using a modified version of the World Health Organization (WHO) worksheet based tool for estimating the economic burden of seasonal influenza. Additionally, we restricted the analysis to influenza-associated severe acute respiratory illness (SARI) and influenza-like illness (ILI; subsets of all-respiratory illnesses) as suggested in the WHO manual. RESULTS: The estimated mean annual cost of influenza-associated illness was $270.5 million, of which $111.3 million (41%) were government-incurred costs, 40.7 million (15%) were out-of-pocket expenses, and $118.4 million (44%) were indirect costs. The cost of influenza-associated medically attended mild illness ($107.9 million) was 2.3 times higher than that of severe illness ($47.1 million). Influenza-associated respiratory illness costs ($251.4 million) accounted for 93% of the total cost. Estimated absenteeism and YLL were 13.2 million days and 304 867 years, respectively. Among patients with influenza-associated WHO-defined ILI or SARI, the costs ($95.3 million), absenteeism (4.5 million days), and YLL (65 697) were 35%, 34%, and 21% of the total economic and health burden of influenza. CONCLUSION: The economic burden of influenza-associated illness was substantial from both a government and a societal perspective. Models that limit estimates to those obtained from patients with WHO-defined ILI or SARI substantially underestimated the total economic and health burden of influenza-associated illness.

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

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.