Evaluation of an influenza-like illness case definition in the diagnosis of influenza among patients with acute febrile illness in cambodia

Abstract

BackgroundInfluenza-like illness (ILI) is often defined as fever (>38.0°C) with cough or sore throat. In this study, we tested the sensitivity, specificity, and positive and negative predictive values of this case definition in a Cambodia patient population.MethodsPassive clinic-based surveillance was established at nine healthcare centers to identify the causes of acute undifferentiated fever in patients aged two years and older seeking treatment. Fever was defined as tympanic membrane temperature >38°C lasting more than 24 hours and less than 10 days. Influenza virus infections were identified by polymerase chain reaction.ResultsFrom July 2008 to December 2008, 2,639 patients were enrolled. From 884 (33%) patients positive for influenza, 652 presented with ILI and 232 acute fever patients presented without ILI. Analysis by age group identified no significant differences between influenza positive patients from the two groups. Positive predictive values (PPVs) varied during the course of the influenza season and among age groups.ConclusionThe ILI case definition can be used to identify a significant percentage of patients with influenza infection during the influenza season in Cambodia, assisting healthcare providers in its diagnosis and treatment. However, testing samples based on the criteria of fever alone increased our case detection by 34%.

Causes of non-malarial fever in Laos: a prospective study

“…Influenza B was the most frequently detected strain (121 [87%]), followed by influenza A subtype H3 (ten [7%]), and pandemic influenza A H1N1 (eight [6%]; appendix). 137 (99%) of 139 patients who tested positive had data to establish whether they had influenza-like illness as defined by WHO 29 . Of these patients, 73 (53%) of those with any influenza, 60 (50%) with influenza B, five (50%) with influenza A subtype H3, and eight (100%) with pandemic H1N1 fulfilled criteria for influenza-like illness.…”

“…As suggested in Cambodia, 50% of cases of influenza B would not have been identified by surveillance for influenza-like illness 29 . At several Cambodian clinics, causes identified for 38% of febrile patients (fever <10 days, aged >2 years) were mainly influenza, dengue, malaria, and typhoid 41 .…”

Temporal aggregation impacts on epidemiological simulations employing microcontact data

“…The Flunet dataset is characterized by a two minute-level temporal contact resolution, and a smaller population (N=36) observed over a much longer time period (T=92 days) than other studies [9,10]. Taking advantage of the longer time duration of this study, we examine agent-based simulation using a previously contributed ILI model [29], and both previously contributed [8,23,24] and novel dynamic network structures, and previously used but unevaluated strategies for extending the study timeframe. We report three important findings:…”

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

“…9 The performance of influenza case definitions has been evaluated many times but only among ambulatory or hospitalized patients with fever or respiratory symptoms. [10][11][12][13][14][15][16][17][18][19][20] Such evaluations may have missed influenza cases with atypical clinical presentations, particularly those caused by acute exacerbations of underlying disease. In the Hong Kong Special Administrative Region of China and in the United States of America, > 75% of all cases of influenza-associated severe disease have been found to be classified not as influenza but under the underlying condition (e.g.…”