Results from a test-and-treat study for influenza among residents of homeless shelters in King County, WA: A stepped-wedge cluster-randomized trial

Influenza Other Respir Viruses. 2023 Jan;17(1):e13092. doi: 10.1111/irv.13092. Epub 2023 Jan 7.


Background: Persons experiencing homelessness face increased risk of influenza as overcrowding in congregate shelters can facilitate influenza virus spread. Data regarding on-site influenza testing and antiviral treatment within homeless shelters remain limited.

Methods: We conducted a cluster-randomized stepped-wedge trial of point-of-care molecular influenza testing coupled with antiviral treatment with baloxavir or oseltamivir in residents of 14 homeless shelters in Seattle, WA, USA. Residents ≥3 months with cough or ≥2 acute respiratory illness (ARI) symptoms and onset <7 days were eligible. In control periods, mid-nasal swabs were tested for influenza by reverse transcription polymerase chain reaction (RT-PCR). The intervention period included on-site rapid molecular influenza testing and antiviral treatment for influenza-positives if symptom onset was <48 h. The primary endpoint was monthly influenza virus infections in the control versus intervention periods. Influenza whole genome sequencing was performed to assess transmission and antiviral resistance.

Results: During 11/15/2019-4/30/2020 and 11/2/2020-4/30/2021, 1283 ARI encounters from 668 participants were observed. Influenza virus was detected in 51 (4%) specimens using RT-PCR (A = 14; B = 37); 21 influenza virus infections were detected from 269 (8%) intervention-eligible encounters by rapid molecular testing and received antiviral treatment. Thirty-seven percent of ARI-participant encounters reported symptom onset < 48 h. The intervention had no effect on influenza virus transmission (adjusted relative risk 1.73, 95% confidence interval [CI] 0.50-6.00). Of 23 influenza genomes, 86% of A(H1N1)pdm09 and 81% of B/Victoria sequences were closely related.

Conclusion: Our findings suggest feasibility of influenza test-and-treat strategies in shelters. Additional studies would help discern an intervention effect during periods of increased influenza activity.

Keywords: antiviral treatment; homeless shelters; influenza; randomized control trial; rapid molecular influenza test.

Publication types

  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, P.H.S.
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antiviral Agents / therapeutic use
  • Humans
  • Ill-Housed Persons*
  • Influenza A Virus, H1N1 Subtype* / genetics
  • Influenza, Human* / diagnosis
  • Influenza, Human* / drug therapy
  • Influenza, Human* / epidemiology
  • Orthomyxoviridae Infections* / drug therapy
  • Oseltamivir / therapeutic use


  • Oseltamivir
  • Antiviral Agents