Risk Of Infectious Disease Transmission Research Articles

Induced mesenchymal stem cells generated from periodontal ligament fibroblast for regenerative therapy

Bone fractures and bone loss represent significant global health challenges, with their incidence rising due to an aging population. Despite autologous bone grafts remain the gold standard for treatment, challenges such as limited bone availability, immune reactions, and the risk of infectious disease transmission have driven the search for alternative cell-based therapies for bone regeneration. Stem cells derived from oral tissues and umbilical cord mesenchymal stem cells (MSCs) have shown potential in both preclinical and clinical studies for bone tissue regeneration. However, their limited differentiation capacity and wound healing abilities necessitate the exploration of alternative cell sources. In this study, we generated induced pluripotent stem cells (iPSCs) using a safe, nonviral and mRNA-based approach from human periodontal ligament fibroblasts (PDLF), an easily accessible cell source. These iPSCs were subsequently differentiated into MSCs, referred to as induced MSCs (iMSCs). The resulting iMSCs were homogeneous, highly proliferative, and possessed anti-inflammatory properties, suggesting their potential as a superior alternative to traditional MSCs for regenerative therapy. These iMSCs demonstrated trilineage differentiation potential, giving rise to osteocytes, chondrocytes, and adipocytes. The iMSC-derived osteocytes (iOSTs) were homogeneous, patient-specific and showed excellent attachment and growth on commercial collagen-based membranes, highlighting their suitability for bone tissue regeneration applications. Given their promising characteristics compared to traditional MSCs, PDLF-derived iMSCs are strong candidates for future clinical studies in bone regeneration and other regenerative dental therapies.

Combined performance of upper-room UVGI and ceiling-mounted air cleaners for removing active bioaerosol

Upper-room ultraviolet germicidal irradiation (UR-UVGI) and ceiling-mounted air cleaner (CM-AC) technologies contribute to curbing the spread of infectious diseases such as COVID-19. However, there is a lack of detailed studies on the performance differences between these two control technologies for reducing viral concentrations and infection risk in isolation ward environments with different ventilation modes, especially when used alone versus in combination. Therefore, this study performed numerical simulations under three ventilation modes, namely, downward ventilation (DWV), stratum ventilation (SV), and displacement ventilation (DV), by the Eulerian-Lagrangian method combined with the UV inactivation model. The viral disinfection performance of UR-UVGI and CM-AC was parametrically analyzed. The effectiveness of the combined application of these two control technologies in wards was evaluated. The results showed that expanding the irradiation range was more effective in enhancing the UR-UVGI performance with the same total UV flux. When using UR-UVGI only, DWV disinfected better at the same irradiation flux. In CM-AC cases, the viral aerosol removal efficiency was the greatest in DV. UR-UVGI and CM-AC had advantages in active bioaerosol removal in overall and localized indoor spaces, respectively. The combined application was recommended to maximize the air cleanliness. Under the role of UR-UVGI, a high level of disinfection could be achieved using CM-AC with low ventilation rates. When the CM-AC ventilation rate was 150 m3/h and the UV irradiance was 30 μW/cm2, the viral disinfection of DV exceeded 90 %, while that of DWV was also close to 90 %. The findings could provide insights to further lower the transmission risk of infectious diseases.

Managing risk of infectious disease transmission at religious mass gatherings.

Managing risk of infectious disease transmission at religious mass gatherings.

Impact of initial outbreak locations on transmission risk of infectious diseases in an intra-urban area

Infectious diseases usually originate from a specific location within a city. Due to the heterogenous distribution of population and public facilities, and the structural heterogeneity of human mobility network embedded in space, infectious diseases break out at different locations would cause different transmission risk and control difficulty. This study aims to investigate the impact of initial outbreak locations on the risk of spatiotemporal transmission and reveal the driving force behind high-risk outbreak locations. First, we built a SLIR (susceptible-latent-infectious-removed)-based age-stratified meta-population model, integrating mobile phone location data, to simulate the spreading process of an infectious disease across fine-grained intra-urban regions (i.e., 649 communities of Shenzhen City, China). Based on the simulation model, we evaluated the transmission risk caused by different initial outbreak locations by proposing three indexes including the number of infected cases (CaseNum), the number of affected regions (RegionNum), and the spatial diffusion range (SpatialRange). Finally, we investigated the contribution of different influential factors to the transmission risk via machine learning models. Results indicate that different initial outbreak locations would cause similar CaseNum but different RegionNum and SpatialRange. To avoid the epidemic spread quickly to more regions, it is necessary to prevent epidemic breaking out in locations with high population-mobility flow density. While to avoid epidemic spread to larger spatial range, remote regions with long daily trip distance of residents need attention. Those findings can help understand the transmission risk and driving force of initial outbreak locations within cities and make precise prevention and control strategies in advance.

Survey of the husbandry and biosecurity practices of backyard chicken keepers in the UK.

This survey investigated the housing, feeding, health and welfare of backyard chickens kept in the UK. Information was collected via an online questionnaire active from May to July 2021. The survey asked about flock demographics, housing, diet, enrichment provision, if the flock was registered with the Animal Plant and Health Agency (APHA) and the reason, preventative health care and biosecurity, and the incidence and methods of euthanasia. The majority of flocks (48.8%) consisted of one to five birds, were located in rural areas (58%) and were kept as pets (77%) and/or for eggs (71.6%). Enrichment was provided by 78.4% of keepers. Most respondents (69%) were aware of the Animal Plant and Health Agency poultry registration scheme, with 32.8% being registered with the scheme. Kitchen scraps were fed by 29% of keepers. Veterinary services were used by 63.6% of keepers, although 4% said they struggled to find a veterinarian willing to treat backyard poultry. New additions to the flock were isolated by 70.2% of keepers. The survey was distributed through poultry-specific Facebook groups and via chicken rescue centres, so it is not a truly random sample of backyard chicken keepers. All survey-based studies have an inherent element of subjectivity. The survey identified biosecurity, humane euthanasia training, veterinary training in backyard poultry medicine, and enrichment provision as areas where improvements can be made to improve poultry health and welfare and reduce the risks of infectious disease transmission.

Statistical analysis of infectious disease transmission risk based on exhaled respiratory droplet trajectory distribution

In the present work, the risk of infectious disease transmission is evaluated based on a statistical analysis of respiratory droplet trajectory distribution. An analytical model recently developed by the authors allows the prediction of the trajectory and evaporation rate of exhaled droplets. The model is used to collect data from a sampling set of more than twenty thousand droplets distributed over a range of diameters from 0.1 μm to 1 mm for different respiratory scenarios. The analytical tool implements the governing equations of droplet transport, evaporation, energy balance, and chemical composition. It also features a two-dimensional unsteady empirical model of respiratory cloud including momentum dissipation and buoyancy. A discrete random walk approach to simulate the droplet turbulent dispersion, and the randomization of the droplet release within the exhalation period and the mouth cross section area complete the model enabling statistical analyses to be rightly performed. With the due boundary conditions, different types of respiratory events can be modeled easily. With additional information on the exhaled droplet size distribution and viral content, spatial maps of virus concentration are derived and associated with the risk of infectious disease transmission being able to discriminate between various transmission routes such as fomite, airborne, or direct inhalation. Different scenarios are presented including mouth breathing, nose breathing, speaking, coughing, and sneezing. The fluid dynamic behavior of respiratory droplets is explored on a size basis, and the role of ventilation discussed. Risk evaluation provides useful information for a knowledgeable discussion on the prevention needs and means from case to case.

Status of zoonotic disease research in refugees, asylum seekers and internally displaced people, globally: A scoping review of forty clinically important zoonotic pathogens.

At the end of 2022, there were over 108 million forcibly displaced people globally, including refugees, asylum seekers (AS) and internally displaced people (IDPs). Forced migration increases the risk of infectious disease transmission, and zoonotic pathogens account for 61% of emerging and re-emerging infectious diseases. Zoonoses create a high burden of disease and have the potential to cause large-scale outbreaks. This scoping review aimed to assess the state of research on a range of clinically relevant zoonotic pathogens in displaced populations in order to identify the gaps in literature and guide future research. Literature was systematically searched to identify original research related to 40 selected zoonotic pathogens of interest in refugees, AS and IDPs. We included only peer-reviewed original research in English, with no publication date restrictions. Demographic data, migration pathways, health factors, associated outbreaks, predictive factors and preventative measures were extracted and synthesized. We identified 4,295 articles, of which 347 were included; dates of publications ranged from 1937 to 2022. Refugees were the most common population investigated (75%). Migration pathways of displaced populations increased over time towards a more complex web, involving migration in dual directions. The most frequent pathogen investigated was Schistosoma spp. (n = 99 articles). Disease outbreaks were reported in 46 publications (13.3%), with viruses being the most commonly reported pathogen type. Limited access to hygiene/sanitation, crowding and refugee status were the most commonly discussed predictors of infection. Vaccination/prophylaxis drug administration, surveillance/screening and improved hygiene/sanitation were the most commonly discussed preventative measures. The current research on zoonoses in displaced populations displays gaps in the spectrum of pathogens studied, as well as in the (sub)populations investigated. Future studies should be more inclusive of One Health approaches to adequately investigate the impact of zoonotic pathogens and identify transmission pathways as a basis for designing interventions for displaced populations.

Managing risk of infectious disease transmission at religious mass gatherings: Insights from survey, COVID-19 PCR, and antibody tests from Arbaeen walkers in 2020.

Arbaeen in Iraq has been one of the largest mass gatherings during the COVID-19 pandemic with 14.5 million attendees in 2020. We set out to assess the prevalence of current or past COVID-19 among 2020 Arbaeen participants, and establish associations between COVID-19 test results, symptoms, and known recent exposure. This was a cross-sectional study involving participants who joined Arbaeen walk in Iraq in October 2020. COVID-19 PCR and/or rapid antibody test were conducted among consented participants. A short questionnaire was administered. Rapid antibody testing was done onsite. Nasal and throat swab samples were transferred to the laboratory for PCR testing. A total of 835 (88.3% male; 11.7% female) participants were recruited. The most common symptom overall was cough (9.6%) followed by sore throat, fever, and loss of taste/smell (6.6%, 5.5%, and 5.0%, respectively). One in five (20.3%) participants reported close contact with a confirmed COVID-19 case in the past 14 days. Of the 237 participants with a PCR test, 18 (7.6%) were positive. Of the 765 participants with rapid antibody test, 19.3% tested positive for IgM, 39.3% for IgG, and 16.4% for both. Approximately 40% of the participants had evidence of current or past COVID-19 infection based on antibody and PCR. The almost 1 in 10 COVID-19 cases within such a multimillion person gathering, illustrates the difficulty in limiting the participation of infectious individuals in religious mass gatherings. There is a pressing need to explore measures to reduce the risk of transmission of infectious diseases at major mass gathering events.

Challenges of Compliance with Infection Prevention and Control (IPC) Standard Procedures among Healthcare Workers: A Hospital-Based Cross-Sectional Study

Introduction: This hospital-based cross-sectional study aimed to assess the compliance of 251 healthcare workers (HCWs) with Infective Prevention and Control (IPC) standard procedures. The study addresses the critical issue of IPC compliance among HCWs, as it plays a pivotal role in reducing the risk of infectious disease transmission within healthcare settings. Methodology: Analytical cross-sectional study was conducted at St. Francis Referral Hospital, involving 251 healthcare workers from different departments including Internal medicine, Surgery, and Emergency. The Compliance with Standard Precautions Scale (CSPS) tool developed by WHO was used. Descriptive and regression analysis was done. A P-value of less than 0.05 indicated statistical significance. Results: Overall average compliance with IPCSPs was 54% whereby only 24.7% (62/251) of healthcare workers had a good compliance. The majority of HCWs (85.3%) reported highest compliance on proper disposal of used sharp items into sharp boxes and low compliance rate (11.6%) was on the disposal of the sharp box, sharp box is only disposed when it is full. Statistically significant were found between IPCSPs and number of years of working experience, level of education, profession, IPC training and IPC meeting attendance. Conclusion: This cross-sectional study has shed light on the critical challenges faced by healthcare workers in complying with IPCSPs. Findings revealed a concerning compliance with IPCSPs which is below the WHO standard and national level standard as well. We therefore recommend enhancement of IPC training program, IPC awareness campaign, and more implementational research for IPCSPs compliance.

Exploring the Effectiveness of Hydrophobic Glass Surface on Touch-Enabled Digital Device to Reduce Microbial Adhesion and Propagation

ABSTRACT This study investigates the effectiveness of hydrophobic glass surfaces in reducing microbial populations on touch-enabled digital devices. Hydrophobic coatings have been proposed as a potential solution to minimize microbial adhesion and growth on device surfaces. Here, we intended to investigate the effect of hydrophobic spray on microbial load. The results were quantitatively analyzed using microbiological techniques. the nonhydrophobic surface harbors gradual microbial buildup upon time, such as threefold increase from 2 to 4 h and fivefold increase to 6 h post initial sampling with 143.6 ± 33.89 cfu/ml increase up to 264.7 ± 28.53 cfu/ml, whereas the hydrophobic surface had an overall build-up from 16.6 ± 1.2 to 50.45 ± 11.12 cfu/ml with P < 0.0001 significance. This research provides valuable insights into the potential application of hydrophobic glass coatings to mitigate microbial contamination on touch-enabled digital devices, enhancing their hygienic properties and minimizing the risk of infectious disease transmission.

Case Management of Imported Crimean-Congo Hemorrhagic Fever, Senegal, July 2023.

We report an imported Crimean-Congo hemorrhagic fever case in Senegal. The patient received PCR confirmation of virus infection 10 days after symptom onset. We identified 46 patient contacts in Senegal; 87.7% were healthcare professionals. Strengthening border crossing and community surveillance systems can help reduce the risks of infectious disease transmission.

Quality of examination gloves in health facilities in Addis Ababa, Ethiopia

Background: Examination gloves are used in health facilities to protect health professionals and patients from the risk of infection and reduce opportunities for cross-transmission of infectious microorganisms. Poor-quality examination gloves can expose health professionals to infectious diseases such as Covid-19, Hepatitis, HIV/AIDS, and other contagious diseases. Hence, this study aimed to assess the quality of examination gloves in health facilities in Addis Ababa.
 Methods: A cross-sectional study design was employed. The examination gloves were collected from randomly selected health facilities in Addis Ababa. The gloves were examined following standard procedure in the Ethiopian Food and Drug Authority. Holes in the examination gloves were detected using the watertight (leakage test) and geometrical dimensions such as thickness, width, and length were measured.
 Results: A total of 2500 selected examination gloves were collected between Feb 10 and Feb 20, 2021. The gloves were sampled from health facilities in Addis Ababa. From the total samples collected, only 2280 examination gloves of five different brands were tested, which makes the response rate 91.2%. The proportion of gloves with holes detected ranged from 5.7% to 21.9%. Overall, only 0.17% and 3.2% of the gloves had width and length below standard, respectively. None of the gloves tested in this study had a thickness below the standard.
 Conclusions: All brands of examination gloves tested had a higher hole (leakage) rate than the acceptable quality limit. This implies there is a substantial risk of infectious disease transmission to health professionals and patients in healthcare settings. Hence, regulatory enforcements need to be strengthened across the life cycle of the product.

Infectious Disease Preparedness for Homeless Populations: Recommendations from a Community–Academic Partnership

Abstract: Background: People experiencing homelessness are at increased risk of infectious disease transmission due to congregate living conditions, barriers to healthcare, and excess burden of underlying chronic disease. Objectives: We are a multisectoral community–academic partnership working to address the intersecting crises of homelessness and health disparities in Tippecanoe County, Indiana. We offer key recommendations for infectious disease preparedness and risk mitigation for homeless populations based on our ongoing community-based participatory research and lessons learned through COVID-19 response and Monkeypox preparations. Lessons Learned: Infectious disease preparedness and response in homeless populations requires strong local partnerships; ongoing training and support for staff and volunteers of homeless shelters and service agencies; tailored outreach, education, and communication with people experiencing homelessness; and standardized processes for creating, disseminating, enforcing, and evaluating public health policies in homeless shelters. Consistency and open communication are key to a successful community-academic partnership. Conclusions: Community–academic partnerships are critical to effective infectious disease preparedness in homeless populations. The lessons learned from community-based participatory research with homeless communities and multisectoral partners on the frontline can improve future outbreak and pandemic response for people experiencing homelessness and other vulnerable communities in the United States.

Availability of basic infection control items and personal protection equipment in 7948 health facilities in eight low- and middle-income countries: Evidence from national health system surveys.

Hundreds of millions of people become infected globally every year while seeking care in health facilities that lack basic needs like infection control measures and personal protective equipment (PPE). We aimed to evaluate the availability of infection control items and PPE in eight low- and middle-income countries and identify disparities in the availability of those items. In this study, we combined publicly available nationally representative cross-sectional health system surveys (Service Provision Assessments by the Demographic and Health Survey Programme) conducted in eight countries between 2013 and 2018: Afghanistan, Bangladesh, the Democratic Republic of the Congo, Haiti, Malawi, Nepal, Senegal, and Tanzania. The availability of infection control items was evaluated using a list of six items (a waste receptacle, a sharps container, disinfectant, single-use disposable or auto-disposable syringes, soap and running water, or an alcohol-based hand rub, and guidelines for standard precautions). PPE includes four items: gloves, medical masks, gowns, and eye protection. We considered these items available in a facility if they were observed in general outpatient areas or any service-specific area (i.e. delivery room). We analysed data from 7948 health facilities (694 hospitals and 7254 health centres/clinics). Overall, among the infection control items and PPE, most surveyed facilities had high availability of single-use disposable or auto-disposable syringes (91.40%) and latex gloves (92.56%). Of infection control measures, guidelines for infection control were the least available during the survey, with the lowest (6.15%) in Nepal and the highest (68.18%) in Malawi. Of the PPE items, eye protection was the least available during the survey, with the lowest (5.4% in Senegal) and the highest (28.17%) in Haiti. Only 1567 (19.71%) facilities looked to have all the basic infection control materials, and 1023 (12.87%) of the analysed facilities possessed all of the PPE. Within the same country, the availability of items varied more between hospitals and health centres/clinics than between them. All eight of our study countries experience shortages of the most fundamental standard precaution items to avert infection. Steps must be taken in each of these countries to reduce inadequacies and disparities and enhance efficiency in the conversion of health-system inputs into the facility's availability of standard precaution items for infection control - to curb the risk of infectious disease transmission.

Ventilation shutdown and the breath-taking violence of infectious disease emergency management in industrial livestock production

Powerful ventilation systems are a crucial technology in industrial livestock production, mitigating the unhealthy ambient conditions that result from great densities of animal bodies, biowastes, and chemical agents, and enabling the rapid production of massive quantities of flesh and eggs in such crowded indoor spaces. But bad air is just one of many biophysical and technoscientific challenges managed in these spaces, chief among them the ever-present risks of infectious disease transmission and evolution that threaten animal health and productivity and pose untold risks for humans. This article examines the intersection of these two central problems, where ventilation systems that are normally used to manage bad air within enclosures have been repurposed in the context of disease outbreaks to quickly and cheaply kill infected populations by hyperthermia. An analysis of this nascent practice, euphemistically termed “ventilation shutdown,” shows how governments and publicly funded scientific institutions have worked with private industry to develop and systematize the use of this and other technologies of mass death to respond to infectious disease emergencies, a dynamic that, we argue, sheds new light on both the precarity and the violence of industrial livestock production.

Advancing indoor risk mapping for virus transmission of infectious diseases through geographic scenario simulation

ABSTRACT Close-range interpersonal interactions serve as a major channel for virus transmission, with higher infection risks indoors than outdoors. Thus, evaluating indoor infectious disease transmission risks is vital for effective epidemic prevention and control. However, collecting complete individual-level behavioral data faces challenges due to privacy concerns and data acquisition costs, impeding accurate indoor risk mapping. To address this, we propose an individual-centered, scenario-based simulation framework in this paper. This framework incorporates stepwise movement of agents to model crowd interactions in indoor spaces, enabling infection risk mapping through geographic scenario simulation. The simulation model’s core components encompass the generation of indoor environments, formulation of individual behavior rules, establishment of human-environment interaction logic, and simulation of virus transmission processes. Additionally, we outline the implementation algorithm for this simulation model. Lastly, we employ a high-risk university canteen as a case study to demonstrate the model’s capabilities in creating risk maps at different levels: spatial, spatiotemporal, and individual. The proposed framework achieves the construction and process simulation of multi-dimensional geographic scenarios at a microscale, introduces a behavior path model based on spatiotemporal cubes, and enhances the comprehensive analysis and mapping capabilities for indoor infectious disease risk, laying the foundation for precise prevention and control.

Airborne transmission risks of tuberculosis and COVID-19 in schools in South Africa, Switzerland, and Tanzania: Modeling of environmental data.

The COVID-19 pandemic renewed interest in airborne transmission of respiratory infections, particularly in congregate indoor settings, such as schools. We modeled transmission risks of tuberculosis (caused by Mycobacterium tuberculosis, Mtb) and COVID-19 (caused by SARS-CoV-2) in South African, Swiss and Tanzanian secondary schools. We estimated the risks of infection with the Wells-Riley equation, expressed as the median with 2.5% and 97.5% quantiles (credible interval [CrI]), based on the ventilation rate and the duration of exposure to infectious doses (so-called quanta). We computed the air change rate (ventilation) using carbon dioxide (CO2) as a tracer gas and modeled the quanta generation rate based on reported estimates from the literature. The share of infectious students in the classroom is determined by country-specific estimates of pulmonary TB. For SARS-CoV-2, the number of infectious students was estimated based on excess mortality to mitigate the bias from country-specific reporting and testing. Average CO2 concentration (parts per million [ppm]) was 1,610 ppm in South Africa, 1,757 ppm in Switzerland, and 648 ppm in Tanzania. The annual risk of infection for Mtb was 22.1% (interquartile range [IQR] 2.7%-89.5%) in South Africa, 0.7% (IQR 0.1%-6.4%) in Switzerland, and 0.5% (IQR 0.0%-3.9%) in Tanzania. For SARS-CoV-2, the monthly risk of infection was 6.8% (IQR 0.8%-43.8%) in South Africa, 1.2% (IQR 0.1%-8.8%) in Switzerland, and 0.9% (IQR 0.1%-6.6%) in Tanzania. The differences in transmission risks primarily reflect a higher incidence of SARS-CoV-2 and particularly prevalence of TB in South Africa, but also higher air change rates due to better natural ventilation of the classrooms in Tanzania. Global comparisons of the modeled risk of infectious disease transmission in classrooms can provide high-level information for policy-making regarding appropriate infection control strategies.

Predicting COVID-19 Outbreaks in Correctional Facilities Using Machine Learning.

The risk of infectious disease transmission, including COVID-19, is disproportionately high in correctional facilities.We used machine learning methods with data collected from 24 prison facilities in the Pennsylvania Department of Corrections to determine which sources of data best predict a coming COVID-19 outbreak in a prison facility.Key predictors included county-level measures of COVID-19, facility population, and the test positivity rate in a facility.Fortifying correctional facilities with the ability to monitor local community rates of infection (e.g., though improved interagency collaboration and data sharing) along with continued testing of incarcerated people and staff can help correctional facilities better predict-and respond to-future infectious disease outbreaks.

The Intelligent Infectious Disease Active Surveillance and early warning system in China: An application of dengue prevention and control

Utilizing advanced information technologies such as big data and artificial intelligence (AI), China has established and implemented the Intelligent Infectious Disease Active Surveillance and Early Warning System. It provides new tools for the surveillance, early warning, and response to infectious diseases, enhancing the timeliness, scientific basis, and efficiency of epidemic control efforts. The system comprises four functional modules including multi-channel active surveillance, intelligent early warning, data-driven risk assessment, and smart emergency response. This paper provides a detailed overview of the structure and functions of the Intelligent Infectious Disease Active Surveillance and Early Warning System in China, with a specific focus on its application in dengue prevention and control in Hainan Province from February to May 2024. Firstly, the system can proactively capture and integrate heterogeneous surveillance data from multiple sources. Based on these multi-channel data, users can select appropriate warning indicators and AI models to automatically trigger early warnings. Using vast amounts of surveillance data, the system can construct machine learning models to accurately assess the transmission risk of infectious diseases. In terms of emergency response, the system offers powerful tools for early diagnosis, smart epidemiological investigation, digital contact tracing, vaccine and drug development, and evaluation of intervention measures. This system facilitates early detection, reporting, and management of outbreaks, serving as a valuable reference for other countries and regions. Nevertheless, continuous efforts are needed to strengthen scientific research and multidisciplinary collaboration, establish reliable data collection mechanisms, enhance continuous model monitoring and adjustments, and leverage the latest large language models. In the future, the system will be further optimized to help control emerging and major infectious diseases more effectively.

Outdoor social distancing behaviors changed during a pandemic: A longitudinal analysis using street view imagery.

Social distancing, defined as maintaining a minimum interpersonal distance (often 6 ft or 1.83 m), is a non-pharmaceutical intervention to reduce infectious disease transmission. While numerous quantitative studies have examined people's social distancing behaviors using mobile phone data, large-scale quantitative analyses of adherence to suggested minimum interpersonal distances are lacking. We analyzed pedestrians' social distancing behaviors of using 3 years of street view imagery collected in a metropolitan city (Seattle, WA, USA) during the COVID-19 pandemic. We employed computer vision techniques to locate pedestrians in images, and a geometry-based algorithm to estimate physical distance between them. Our results indicate that social distancing behaviors correlated with key factors such as vaccine availability, seasonality, and local socioeconomic data. We also identified behavioral differences at various points of interest within the city (e.g., parks, schools, faith-based organizations, museums). This work represents a first of its kind longitudinal study of outdoor social distancing behaviors using computer vision. Our findings provide key insights for policymakers to understand and mitigate infectious disease transmission risks in outdoor environments.