Evaluation of COVID-19 and Influenza-like Illness Surveillance Case Definitions in a Prospective Cohort of Healthcare Personnel in Peru.

Abstract

Public health agencies employ case definitions for influenza virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections to optimize surveillance, monitor disease trends, and inform decision-making, particularly in limited resource settings. Using a prospective healthcare personnel cohort in two hospitals in Lima, Peru (July 2022-June 2023), we compared and evaluated the performance of three symptom profiles of three common surveillance case definitions to identify influenza and SARS-CoV-2 infections: influenza-like illness, coronavirus disease 2019-like illness (CLI), and acute respiratory infection. Participants with an acute respiratory illness reported symptom progression twice weekly. Participants self-collected nasal swabs for SARS-CoV-2 and influenza reverse transcription real-time polymerase chain reaction testing. Sensitivity, specificity, and positive and negative predictive values of each case definition were evaluated. Of 1623 participants enrolled, 1450 illness episodes were reported; 92 (6%) were positive for influenza, 350 (24%) for SARS-CoV-2, and 3 (0.2%) were positive for both. For the four influenza-like illness case definitions evaluated, all yielded low sensitivity for detection of influenza (points estimate range, 23%-35%) and SARS-COV-2 (range, 21%-29%), but high specificity (83%-90% and 86%-92%, respectively). In contrast, the acute respiratory infection and coronavirus disease 2019-like illness definitions both yielded high sensitivity (83%-100%) and low specificity (2%-41%) for detection of both influenza and SARS-CoV-2. The performance of case definitions was similar for influenza and SARS-CoV-2 supporting the use of the same definitions by surveillance networks. The substantial differences in sensitivity and specificity across the case definitions necessitate surveillance objectives and cost considerations in selecting a case definition fit for purpose.