Performance of case definitions used for influenza surveillance among hospitalized patients in a rural area of India

Incidence of influenza-associated hospitalization in rural communities in western and northern India, 2010–2012: A multi-site population-based study

“…In a previous analysis from the same study, we showed that the sensitivity of original WHO ILI case definition was 78% in Ballabgarh and 87% in Vadu and we would accordingly underestimated the burden had we used the ILI case definition to estimate influenza-associated hospitalization incidence in our study. 17,18 The observed differences in influenza-associated hospitalization incidences between sites in our study could have been partially explained by differences in influenza circulation and transmission. Data from influenza sentinel surveillance conducted at Delhi, the closest city to Ballabgarh, and Pune, the closest city to Vadu, consistently indicated higher levels of influenza virus detection during our study period suggesting that there were true differences in influenza virus circulation and transmission between northern and western India during this time.…”

Viral etiology in adult influenza-like illness/acute respiratory infection and predictivity of C-reactive protein

“…Characteristics of influenza A/B detected patients are shown in Table 2. The mean (SD) age was 34 (13). The most frequent symptom was coryza (87.1%), followed by malaise (74.2%).…”

“…Case definitions yielded variable performance for influenza surveillance, which would be probably best optimized according to the objectives of the program [8,[11][12][13]. We designed this study to evaluate the viral and bacterial etiology as well as clinical and laboratory characteristics of adult outpatients presenting with ARI/ILI in the winter season of 2013-2014…”

Is influenza-like illness a useful concept and an appropriate test of influenza vaccine effectiveness?

“…For children <5 years the SARI definition had a very low sensitivity of 11% and a high specificity of 87%. If shortness of breath was omitted sensitivity increased to 69% and specificity decreased to 43%, if reported fever was allowed sensitivity increased to 87% and specificity decreased to 5%, and if cough was added sensitivity decreased to 77% but specificity increased to 33% [14]. A study of the H1N1 epidemic in Singapore June-October 2009 found paired samples from 727 ILI cases yielded an influenza estimate of 17% (Bayesian CIs 14-20%) and an average of baseline and final samples a rate of 15% (BCI 10 to 25%) [15].…”