Results from a test-and-treat study for influenza among residents of
homeless shelters in King County, WA: a stepped-wedge cluster-randomized
trial.
Abstract
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 remains 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 RT-PCR.
The intervention period included on-site rapid molecular influenza
testing and antiviral treatment for influenza-positives if symptom onset
was <48 hours. The primary endpoint was monthly influenza
virus infections in the control versus intervention period. 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, 1,283 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%) of intervention-eligible encounters by rapid molecular testing
and received antiviral treatment. 37% of ARI-participant encounters
reported symptom onset <48 hours. The intervention had no
effect on influenza virus transmission (adjusted relative risk 1.73,
95% 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