Novel Use of Rapid Antigen Influenza Testing in the Outpatient Setting as an Early Warning Sign of Influenza Activity in the Emergency Departments of an Integrated Health System.

Larkin, Paige M K; Manuel, Vladimir; Hernandez, Naureen; Garner, Omai B

Seasonal influenza virus is associated with high morbidity and mortality especially in vulnerable patient populations. Here we demonstrate the novel use of Sofia Influenza A + B FIA, a rapid antigen-based influenza point-of-care test (POCT), combined with Virena software for automatic de-identified tracking of influenza activity across the Los Angeles area and for predicting surges of influenza cases in the emergency department (ED). We divided outpatient clinics into 6 geographic zones and compared weekly influenza activity. In the outpatient setting, there were 1,666 and 274 influenza A and influenza B positives, respectively, across the 2018-2019 influenza season and 1,857 and 1,449 influenza A and influenza B positives, respectively, during the 2019-2020 influenza season, with zone-specific differences observed. Moreover, we found that a rapid increase in outpatient influenza was followed by an influx in influenza positive cases in the ED, offering a 1-3 week warning sign for ED influx of triple or quadruple the number of influenza cases compared to the prior week. Sofia Influenza A + B FIA allows for surveillance of real-time deidentified influenza activity. Tracking of such data may serve as a valuable region-specific influenza indicator and predictor to guide infection prevention measures in both the outpatient and hospital settings. High impact interventions include designating areas of waiting rooms for influenza-like illnesses, altering staff scheduling in anticipation of surges, and securing sufficient personal protective equipment and antivirals during the height of influenza season.