Journal Article

Comparison of infection control strategies to reduce COVID-19 outbreaks in homeless shelters in the United States: a simulation study

Chapman, Lloyd A. C., Imbert, Elizabeth, Nguyen, Trang Q., Scarborough, Ashley, Cawley, Caroline, Lo, Nathan C., Cox, Sarah N., Greenhouse, Bryan, Rodriguez-Barraquer, Isabel, Kushel, Margot

2021

Overview

Background COVID-19 outbreaks have occurred in homeless shelters across the US, highlighting an urgent need to identify the most effective infection control strategy to prevent future outbreaks. Methods We developed a microsimulation model of SARS-CoV-2 transmission in a homeless shelter and calibrated it to data from cross-sectional polymerase chain reaction (PCR) surveys conducted during COVID-19 outbreaks in five homeless shelters in three US cities from March 28 to April 10, 2020. We estimated the probability of averting a COVID-19 outbreak when an exposed individual is introduced into a representative homeless shelter of 250 residents and 50 staff over 30 days under different infection control strategies, including daily symptom-based screening, twice-weekly PCR testing, and universal mask wearing. Results The proportion of PCR-positive residents and staff at the shelters with observed outbreaks ranged from 2.6 to 51.6%, which translated to the basic reproduction number ( R 0 ) estimates of 2.9–6.2. With moderate community incidence (~ 30 confirmed cases/1,000,000 people/day), the estimated probabilities of averting an outbreak in a low-risk ( R 0 = 1.5), moderate-risk ( R 0 = 2.9), and high-risk ( R 0 = 6.2) shelter were respectively 0.35, 0.13, and 0.04 for daily symptom-based screening; 0.53, 0.20, and 0.09 for twice-weekly PCR testing; 0.62, 0.27, and 0.08 for universal masking; and 0.74, 0.42, and 0.19 for these strategies in combination. The probability of averting an outbreak diminished with higher transmissibility ( R 0 ) within the simulated shelter and increasing incidence in the local community. Conclusions In high-risk homeless shelter environments and locations with high community incidence of COVID-19, even intensive infection control strategies (incorporating daily symptom screening, frequent PCR testing, and universal mask wearing) are unlikely to prevent outbreaks, suggesting a need for non-congregate housing arrangements for people experiencing homelessness. In lower-risk environments, combined interventions should be employed to reduce outbreak risk.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Biomedicine / Cities - epidemiology / Cities - statistics & numerical data / Computer Simulation - statistics & numerical data / Control / Coronaviruses / COVID-19 / COVID-19 - epidemiology / COVID-19 - prevention & control / COVID-19 Nucleic Acid Testing - methods / COVID-19 Nucleic Acid Testing - statistics & numerical data / Cross-Sectional Studies / Disease control / Disease Outbreaks - prevention & control / Disease Outbreaks - statistics & numerical data / Disease transmission / Epidemics / Health aspects / Homeless people / Homeless shelters / Homelessness / Housing / Housing - statistics & numerical data / Humans / Ill-Housed Persons - statistics & numerical data / Infection control / Infection Control - methods / Infection Control - statistics & numerical data / Infections / Mass Screening - methods / Mass Screening - statistics & numerical data / Medicine / Medicine & Public Health / Methods / Outbreaks / Polymerase chain reaction / Population / Research Article / Risk / Safety and security measures / SARS-CoV-2 / Screening / Severe acute respiratory syndrome coronavirus 2 / Shelters / Simulation / United States / United States - epidemiology / Viral diseases