Homelessness and Infectious Diseases: Understanding the Gaps and Defining a Public Health Approach: Introduction

In the United States, over 1.4 million people are estimated to access homeless services each year [1]. During their experience of homelessness, each of these people may face an increased risk of infectious diseases for several reasons. Homeless services are often provided in congregate facilities, and there may be little choice of with whom you spend time in close contact. Publicly available handwashing sinks can be difficult to locate and may be closed or lacking supplies. For people sleeping outside, bathrooms and showers can also be difficult to find on a regular basis. Additionally, many people experiencing homelessness have underlying medical conditions that can increase their risk of complications or substance use disorders that can put them at risk for drug-related infectious diseases [2]. The risks of human immunodeficiency virus (HIV), tuberculosis, and hepatitis C associated with homelessness have been well described [3–5]. For each of these, homelessness has been shown to contribute substantially to the population burden of disease [6–8]. However, significant gaps related to homelessness and infectious disease still remain in the scientific literature. Furthermore, the coronavirus disease 2019 (COVID-19) pandemic has highlighted the need for improved understanding of the infectious disease risks associated with homelessness to create a more equitable future. The authors who contributed to this supplement provide critical data related to the infectious disease risks faced by people experiencing homelessness, as well as solutions for how to overcome these risks. Four articles in this supplement describe the epidemiology of specific infectious diseases among people experiencing homelessness. In Seattle, Chow et al found consistent circulation of rhinovirus in 9 homeless shelters throughout the COVID-19 pandemic [9]. Their genomic analysis suggests that spread of rhinovirus within the shelters and new introductions into shelters are common. The study highlights the unique public health challenges related to respiratory infectious diseases in congregate settings. In Denver, Shepard et al show an overwhelming burden of an infection thought rare in the United States, Bartonella quintana, among people experiencing homelessness [10]. Patients experiencing homelessness and those with substance use disorders were at highest risk of infection, and, as the authors highlight, often lack access to the health care resources for the management of chronic infection. The authors recommend that clinicians who treat people experiencing homelessness consider screening for B. quintana. Rudmann et al provide a national examination of Neisseria meningiditis that shows the value of having an indicator for housing status in surveillance systems [11]. The analysis shows a large disparity in the risk of invasive meningococcal disease among people experiencing homelessness compared to the general population. The authors suggest that assessment of the feasibility and potential impact of routine meningococcal vaccination for people experiencing homelessness would be an important next step. Finally, Jones et al conducted COVID-19 surveillance in Los Angeles County by pairing multiple data sources including from the Homeless Management Information System (HMIS) and LA County Public Health Department [12]. The authors found that interoperability between distinct data sources was key in understanding COVID-19 and that no single data source was complete for COVID-19 surveillance among people experiencing homelessness. Three articles in the supplement provide information on vaccination coverage and effective vaccine outreach for people experiencing homelessness. In Wisconsin, Gibson et al use a process to integrate data from the state vaccine registry and a database documenting homeless service access [13]. This allowed the authors to examine the coverage of COVID-19 vaccination between people experiencing homelessness and the general population, finding a large disparity between the two. The authors describe that their findings highlight an urgent need for better understanding of barriers to vaccine uptake to improve vaccination coverage among all people experiencing homelessness, but also that, because of the low coverage, continuing shelter-specific infection control strategies are critical to reducing COVID-19 transmission. Allen et al provide a multicity qualitative examination of the best communication pathways to reach people experiencing homelessness with information related to infectious disease prevention, including vaccine promotion [14]. The authors emphasize the role of health care providers collaborating with public health agencies to ensure infectious disease prevention messages are consistent, provided by trusted messengers, multimodal, and paired with other resources that people experiencing homelessness need to protect themselves. Finally, in Los Angeles, Shover et al showed that trusted vaccine ambassadors can be recruited among people experiencing homelessness on the day of vaccination events [15]. These same-day peer ambassadors added value for the community and accounted for over 25% of vaccines provided. This model highlights the important role that people with lived experience plays in health communications and has the potential to improve delivery of other services in addition to vaccination. An article from San Francisco focuses on improving clinical care. Hickey et al describe a pop-up clinic that allowed walk-in access to HIV primary care [16]. The clinic enrolled people who did not have viral suppression and, by the end of the evaluation period, 44% had achieved viral suppression. This clinic was a promising model to improve care engagement and could be used for other infectious diseases in addition to HIV. Finally, an article from New York City highlights the importance of housing as health care [17]. Miller-Archie et al showed a marked impact of permanent supportive housing on outcomes and health care utilization for people with hepatitis C infection, demonstrating that the most critical need for people experiencing homelessness is housing. In the study, permanent supportive housing reduced the number of liver-related hospital admissions, emergency department visits, and mortality among persons infected with hepatitis C. The articles in this supplement provide data related to the context and risks of homelessness, but they also provide hope and motivation for the types of successful interventions that can reach people experiencing homelessness. Effective surveillance systems that are interoperable and adaptable for use in nontraditional settings are crucial to implementing appropriate and effective public health intervention strategies. Health care interventions that reach people where they live are instrumental in improving infectious and chronic disease management and reduce not only the burden of disease, but also the spread. While this supplement is specific to the health challenges faced by people experiencing homelessness, the lessons learned may be applicable to a wide array of populations experiencing or at risk for health inequities. Disclaimer. The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. Financial support. No financial support was received for this work. Supplement sponsorship. This article appears as part of the supplement “Homelessness and Infectious Diseases: Understanding the Gaps and Defining a Public Health Approach,” sponsored by the Centers for Disease Control and Prevention.