DISCUSSION
illness, ARI, infections, infection, transiency
VIRUS, VIRUS INFECTION, SPECIFIC VIRAL INFECTIONS, INFECTIONS, INFECTION, SECONDARY, APPENDIX, INFLUENZA
This study assessed the feasibility and impact of an on‐site test‐and‐treat intervention for influenza among persons experiencing homelessness in a congregate setting. Although the study was limited by operational futility from a near absence of influenza virus circulation in WA in Year 2,Using on‐site surveillance, we observed a substantial proportion of overall ARI encounters (37.4%) within 48 h, a group that would be eligible to receive antiviral treatment if influenza‐positive. The COVID‐19 pandemic has also shown that rapid viral testing at shelters is feasible and effective when combined with mitigation measures; however, the impact of using antivirals for influenza treatment and chemoprophylaxis to reduce intra‐shelter transmission has not yet been explored.A majority of RT‐PCR influenza‐positive participants identified during intervention periods received antiviral treatment (59.4%), suggesting that immediate treatment is feasible. Use of single‐dose baloxavir treatment in this study was an advantage as it was compliance independent and has shown to be effective as both a prophylactic and means of reducing secondary influenza transmission in households.We found that less than half of symptomatic influenza virus infections met ILI criteria. This suggests that the ILI definition is less valuable as a diagnostic criterion than a means of surveilling community‐level influenza virus circulation and that viral diagnostic testing is needed to distinguish signs and symptoms caused by specific viral infections. Based on the World Health Organization (WHO) global influenza update from June 2022, countries are recommended to prepare for the co‐circulation of influenza and SARS‐CoV‐2 viruses and to enhance integrated surveillance to monitor influenza and SARS‐CoV‐2 simultaneously.In this study, rapid influenza molecular testing had high concordance with RT‐PCR results, supporting use in shelters (see Appendix We found that sequenced influenza viruses from the same shelter were frequently closely related, likely reflective of intra‐shelter transmission. However, there were two examples of genetic diversity among samples collected from a single shelter over a short time period, both from family shelters, raising the possibility of multiple influenza viral introductions.Individuals frequently sought clinical care for their ARI in this study, yet few were prescribed an antiviral prior to study enrollment. This may be due to lack of provider awareness regarding antiviral treatment, or delays in seeking clinical care outside of the shelter setting making outside the recommended 48‐h window for antiviral treatment since symptom onset.This study was subject to several limitations. First, the COVID‐19 pandemic and subsequent reduction of influenza virus circulation led to low study power and limited ability to assess the effect of the intervention. We therefore view these results as inconclusive rather than negative. Second, the use of shelter capacity to determine persons at risk in the GLMM calculation does not account for resident transiency and may have over‐estimated the population if shelters were not at maximum capacity during study Year 1. Third, selection biases may have occurred as the nature of the stepped‐wedge cluster‐randomized trial design does not allow for blinding of the intervention. Study participation may have been perceived as more desirable during intervention periods when immediate testing results and actionable intervention for illness episodes were made available. Fourth, our study design may have under‐estimated influenza virus transmission in shelters as we did not assess transmission from residents with asymptomatic infection or capture secondary asymptomatic infections. Finally, survey data were based on self‐report, which may be subjective particularly for variables such as symptoms experienced and illness duration.