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

Abstract

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.

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

“…Influenza virus infection has been reported also among patients hospitalized for respiratory illness that do not meet the SARI case definition. Specifically in a study conducted in South Africa, influenza virus was detected in 5.8% of patients hospitalized with respiratory illnesses that did not meet the SARI case definition 25. Last, ecological studies have suggested that influenza virus is responsible for hospitalizations and deaths also among patients presenting with circulatory illnesses or even syndromes different than respiratory and circulatory 23, 26.…”

The national burden of influenza‐associated severe acute respiratory illness hospitalization in Rwanda, 2012‐2014

“…Influenza virus infection has been reported also among patients hospitalized for respiratory illness that do not meet the SARI case definition. Specifically in a study conducted in South Africa, influenza virus was detected in 5.8% of patients hospitalized with respiratory illnesses that did not meet the SARI case definition 24. In addition, ecological studies have suggested that influenza virus is responsible for hospitalizations and deaths also among patients presenting with circulatory illnesses or even non‐respiratory and non‐circulatory syndromes 5, 6, 19.…”

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

“…The procedures of these surveillance programs have been previously described . In brief, study staff completed case report forms for all enrolled ILI, SARI‐10, and SCRI‐10 cases.…”

“…In brief, we estimated the overall and age‐specific rates of influenza‐associated SARI‐10 hospitalizations per 100 000 population using the number of SARI‐10 hospitalizations, adjusting for non‐enrollment (refusal to participate and non‐enrollment during weekends), healthcare‐seeking behavior in the surveyed community, and the INF‐AF during 2013‐2015. The INF‐AF was obtained from published estimates derived from the same sentinel sites and study period …”

“…Although the wide use of PCR assays has increased diagnostic and surveillance capacity, establishing a clinical association between pathogen detection and illness remains challenging. A study conducted in South Africa suggested that the attributable fraction (AF) of influenza virus detection to mild and severe respiratory illness (referred to as INF‐AF hereafter) varies by age group and HIV serostatus . However, the effect of the INF‐AF on influenza disease burden estimates has not been fully investigated.…”