Epidemiologic Characteristics of Mpox among People Experiencing Homelessness, Los Angeles County, California, USA, 2022.

In Los Angeles County, California, USA, public health surveillance identified 118 mpox cases among persons experiencing homelessness (PEH) during July-September 2022. Age and sex were similar for mpox case-patients among PEH and in the general population. Seventy-one (60%) PEH mpox case-patients were living with HIV, 35 (49%) of them virally suppressed. Hospitalization was required for 21% of case-patients because of severe disease. Sexual contact was likely the primary mode of transmission; 84% of patients reported sexual contact <3 weeks before symptom onset. PEH case-patients lived in shelters, encampments, cars, or on the street, or stayed briefly with friends or family (couch surfed). Some case-patients stayed at multiple locations during the 3-week incubation period. Public health follow-up and contact tracing detected no secondary mpox cases among PEH in congregate shelters or encampments. Equitable efforts should continue to identify, treat, and prevent mpox among PEH, who often experience severe disease.

A COVID-19 Vaccination Program to Promote Uptake and Equity for People Experiencing Homelessness in Los Angeles County.

People experiencing homelessness (PEH) have been disproportionately affected by COVID-19, yet their vaccination coverage is lower than is that of the general population. We implemented a COVID-19 vaccination program that used evidence-based and culturally tailored approaches to promote vaccine uptake and equity for PEH in Los Angeles County, California. From February 2021 through February 2022, 33 977 doses of vaccine were administered at 2658 clinics, and 9275 PEH were fully vaccinated. This program may serve as a model for future service delivery in vulnerable populations. (Am J Public Health. 2023;113(2):170-174. https://doi.org/10.2105/AJPH.2022.307147).

Correlates of SARS-CoV-2 anti-RBD IgG antibody titers among persons experiencing homelessness in Los Angeles.

OBJECTIVES: People experiencing homelessness (PEH) have been especially impacted by the COVID-19 pandemic, likely due to increased vulnerabilities stemming from chronic diseases, substance use, and mental health conditions. DESIGN: A case-control study to assess the presence of antibodies against SARS-CoV-2 among PEH and associations with key variables. SAMPLE: A convenience sample of 97 PEH in Skid Row, Los Angeles. MEASUREMENTS: A structured questionnaire assessing socio-demographic, mental health, drug and alcohol use, health care access, pandemic stress, and other COVID-19-specific questions. RESULTS: We found high anti-receptor binding domain (RBD) IgG titers among five of 15 PEH who reported no prior COVID-19 diagnosis or being vaccinated, suggesting undiagnosed and/or asymptomatic COVID-19. While anti-RBD IgG titers across vaccination categories were not statistically significant (p = .069), participants vaccinated with Janssen had the lowest mean anti-RBD IgG titers. In multivariable analysis, we found negative associations between level of SARS-CoV-2 antibody titers with the Janssen vaccine and depression; thus, a need for integrated care for PEH with depression and COVID-19. CONCLUSIONS: Further research is warranted to confirm the immune response, initial and over time, to SARS-CoV-2 infection and to COVID-19 vaccinations, particularly among PEH whose immune systems may be impacted by multiple health conditions.

Evaluation of the Homeless Management Information System for COVID-19 Surveillance Among People Experiencing Homelessness.

BACKGROUND: Variable and incomplete reporting of housing status creates challenges in the surveillance of coronavirus disease 2019 (COVID-19) among the homeless population in Los Angeles County (LA County) and nationwide. METHODS: We developed standard investigation procedures to assess the housing status of LA County COVID-19 patients. Using data sharing procedures, we matched COVID-19 patients to Homeless Management Information System (HMIS) client profiles and supplemented with additional data sources for contributory data points and to further housing status ascertainment. RESULTS: We identified 10 586 COVID-19 patients among people experiencing homelessness (PEH) between 30 March 2020 and 30 December 2021; 2801 (26.5%) patients were first identified from HMIS profile matches, 1877 (17.7%) from quarantine/isolation housing intake rosters, 573 (5.4%) from hospital records, 749 (7.1%) from case and contact interviews, 3659 (34.6%) directly from PEH medical and service providers, and 927 (8.8%) had unknown sources. Among COVID-19 patients matched to HMIS profiles, 5351 (42.5%) were confirmed to be PEH at the time of COVID-19 diagnosis. CONCLUSIONS: Interoperability between public health data, HMIS, and external partners have been critical components in evaluating the impact of COVID-19 among the LA County homeless population. No one data source was complete for COVID-19 surveillance in this population.

Engaging Same-Day Peer Ambassadors to Increase Coronavirus Disease 2019 Vaccination Among People Experiencing Unsheltered Homelessness in Los Angeles County: A Hybrid Feasibility-Evaluation Study.

BACKGROUND: This study aimed to evaluate the feasibility and acceptability of engaging unhoused peer ambassadors (PAs) in coronavirus disease 2019 (COVID-19) vaccination efforts to reach people experiencing unsheltered homelessness in Los Angeles County. METHODS: From August to December 2021, vaccinated PAs aged ≥18 years who could provide informed consent were recruited during vaccination events for same-day participation. Events were held at encampments, service providers (eg, housing agencies, food lines, and mobile showers), and roving locations around Los Angeles. PAs were asked to join outreach alongside community health workers and shared their experience getting vaccinated, receiving a $25 gift card for each hour they participated. Postevent surveys evaluated how many PAs enrolled and how long they participated. In October 2021, we added a preliminary effectiveness evaluation of how many additional vaccinations were attributable to PAs. Staff who enrolled the PAs estimated the number of additional people vaccinated because of talking with the PA. RESULTS: A total of 117 PAs were enrolled at 103 events, participating for an average of 2 hours. At events with the effectiveness evaluation, 197 additional people were vaccinated over 167 PA hours ($21.19 gift card cost per additional person vaccinated), accounting for >25% of all vaccines given at these events. DISCUSSION: Recruiting same-day unhoused PAs is a feasible, acceptable, and preliminarily effective technique to increase COVID-19 vaccination in unsheltered settings. The findings can inform delivery of other health services for people experiencing homelessness.

COVID-19 Vaccine Acceptability and Financial Incentives among Unhoused People in Los Angeles County: a Three-Stage Field Survey.

Unhoused people have higher COVID-19 mortality and lower vaccine uptake than housed community members. Understanding vaccine hesitancy among unhoused people is key for developing programs that address their unique needs. A three-round, rapid, field-based survey was conducted to describe attitudes toward COVID-19 vaccination. Round 1 assessed vaccine brand preference, round 2 assessed intention to accept a financial incentive for vaccination, and round 3 measured vaccine uptake and assessed reasons for vaccine readiness during implementation of a financial incentive program. A total of 5177 individuals were approached at COVID-19 vaccination events for unhoused people in Los Angeles County from May through November 2021. Analyses included 4949 individuals: 3636 (73.5%) unsheltered and 1313 (26.5%) sheltered. Per self-report, 2008 (40.6%) were already vaccinated, 1732 (35%) wanted to get vaccinated, 359 (7.3%) were not yet ready, and 850 (17.2%) did not want to get vaccinated. Brand preference was evenly split among participants (Moderna 31.0%, J&J 35.5%, either 33.5%, p = 0.74). Interest in a financial incentive differed between those who were not yet ready and those who did not want to get vaccinated (43.2% vs. 16.2%, p < 0.01). After implementing a financial incentive program, 97.4% of participants who indicated interest in vaccination were vaccinated that day; the financial incentive was the most cited reason for vaccine readiness (n = 731, 56%). This study demonstrated the utility of an iterative, field-based assessment for program implementation during the rapidly evolving pandemic. Personal engagement, a variety of brand choices, and financial incentives could be important for improving vaccine uptake among unhoused people.

Nurse-led intervention to decrease drug use among LTBI positive homeless adults.

BACKGROUND: People experiencing homelessness (PEH) are disproportionately diagnosed with active tuberculosis. While promoting latent tuberculosis infection (LTBI) treatment has been a call to action, PEH engaging in substance use often experience challenges in completing LTBI treatment. METHODS: In this non-randomized single arm study, we tested an innovative, community-based, nurse-led community health worker (RN-CHW) model, on reducing drug use among 50 PEH, residing in homeless shelters or living on the streets in Los Angeles. Follow-up was at 3- and 6- months. RESULTS: Findings revealed significant and ongoing decrease in any drug use (odds ratio [OR] = 0.30; 95% confidence interval [CI] = 0.14-0.68); p = .004), amphetamine use (OR = 0.14; 95% CI = 0.02-0.81; p = .029), cannabis use (OR = 0.26; 95% CI = 0.12-0.57; p = .001) and methamphetamine use (OR = 0.30; 95% CI = 0.10-0.90; p = .031) at 6-month follow-up. CONCLUSIONS: To our knowledge, this pilot study is the first to evaluate the impact a RN-CHW delivered intervention on reduction in drug use among PEH enrolled in a LTBI intervention. LTBI interventions may serve as an entryway into reduction in drug use among this underserved population.

Effect of a Nurse-Led Community Health Worker Intervention on Latent Tuberculosis Medication Completion Among Homeless Adults.

BACKGROUND: Tuberculosis (TB) disproportionately affects marginalized and impoverished homeless adults. Although active TB can be prevented by treating latent TB infection (LTBI), individual factors, such as high prevalence of depression and anxiety, drug and alcohol use, and unstable housing, lead to poor LTBI treatment adherence and completion among homeless adults. OBJECTIVES: We hypothesized that the delivery of a tailored nurse-led, community health worker (RN/CHW) program across the LTBI continuum of care (e.g., screening, diagnosis, and treatment) that delivers 3HP treatment (3HP: rifapentine plus isoniazid) for homeless adults (e.g., sheltered and unsheltered) and is tailored to their health and social service needs will overcome existing treatment completion barriers. We also hypothesized that mental health symptoms (e.g., depression and anxiety), drug use score, and problematic alcohol use will decline over time among clients receiving this treatment. METHODS: We assessed the effect of delivering a theoretically guided, RN/CHW-based, single-arm study among eligible LTBI-positive homeless adults (N = 50) on completion of a weekly, directly observed, 12-dose 3HP LTBI treatment in Central City East (Skid Row). Completing 3HP treatment was compared to the only known historical, clinic-based control that obtained 65% completion among homeless adults. Secondary outcomes included drug and alcohol use, depression, and anxiety. RESULTS: The RN/CHW program achieved a 91.8% 3HP treatment completion rate among homeless adults. Younger homeless adults (<50 years old) were less likely to complete 3HP treatment compared to those who were older. Neither drug use, depression, nor anxiety was associated with 3HP treatment completion. Decrease in anxiety was observed at 3 months, but not at 6 months, compared to baseline. DISCUSSION: To our knowledge, the pilot study is the first to evaluate an effective RN/CHW-delivered, community-based intervention, which can reduce the burden of active TB for homeless adults.

Spatial distribution of tuberculosis incidence in Los Angeles County.

BACKGROUND: In Los Angeles County, the tuberculosis (TB) disease incidence rate is seven times higher among non-U.S.-born persons than U.S.-born persons and varies by country of birth. But translating these findings into public health action requires more granular information, especially considering that Los Angeles County is more than 4000 mile2. Local public health authorities may benefit from data on which areas of the county are most affected, yet these data remain largely unreported in part because of limitations of sparse data. We aimed to describe the spatial distribution of TB disease incidence in Los Angeles County while addressing challenges arising from sparse data and accounting for known cofactors. METHODS: Data on 5447 TB cases from Los Angeles County were combined with stratified population estimates available from the 2005-2011 Public Use Microdata Survey. TB disease incidence rates stratified by country of birth and Public Use Microdata Area were calculated and spatial smoothing was applied using a conditional autoregressive model. We used Bayesian Poisson models to investigate spatial patterns adjusting for age, sex, country of birth and years since initial arrival in the U.S. RESULTS: There were notable differences in the crude and spatially-smoothed maps of TB disease rates for high-risk subgroups, namely persons born in Mexico, Vietnam or the Philippines. Spatially-smoothed maps showed areas of high incidence in downtown Los Angeles and surrounding areas for persons born in the Philippines or Vietnam. Areas of high incidence were more dispersed for persons born in Mexico. Adjusted models suggested that the spatial distribution of TB disease could not be fully explained using age, sex, country of birth and years since initial arrival. CONCLUSIONS: This study highlights areas of high TB incidence within Los Angeles County both for U.S.-born cases and for cases born in Mexico, Vietnam or the Philippines. It also highlights areas that had high incidence rates even when accounting for non-spatial error and country of birth, age, sex, and years since initial arrival in the U.S. Information on spatial distribution provided here complements other descriptions of local disease burden and may help focus ongoing efforts to scale up testing for TB infection and treatment among high-risk subgroups.

Exploring the Perspectives of Unhoused Adults and Providers Across the HCV Care Continuum.

Hepatitis C virus (HCV), the most common blood-borne infection, disproportionately affects people experiencing homelessness (PEH); however, HCV interventions tailored for PEH are scarce. This study utilized a community-based participatory approach to assess perceptions of HCV treatment experiences among HCV-positive PEH, and homeless service providers (HSP) to develop and tailor the "I am HCV Free" intervention which integrates primary, secondary, and tertiary care to attain and maintain HCV cure. Four focus groups were conducted with PEH (N = 30, Mage = 51.76, standard deviation 11.49, range 22-69) and HSPs (n = 10) in Central City East (Skid Row) in Los Angeles, California. An iterative, thematic approach was used to ensure the trustworthiness of the data. Barriers and facilitators emerged from the data which have the potential to impact initiating HCV treatment and completion across the HCV care continuum. Understanding and addressing barriers and strengthening facilitators to HCV treatment will aid in HCV treatment completion and cure for PEH.

House calls by community health workers and public health nurses to improve adherence to isoniazid monotherapy for latent tuberculosis infection: a retrospective study.

BACKGROUND: Patient adherence to isoniazid (INH) monotherapy for latent tuberculosis infection (LTBI) has been suboptimal despite its proven efficacy. Various strategies have been studied to improve adherence, but all have been based at a clinic or treatment program. At the Santa Clara Valley Tuberculosis Clinic, it was our practice to refer a subset of high-risk LTBI patients to the Public Health Department for monthly follow-up at home instead of at the clinic. Our goal was to assess whether house calls by community health workers and public health nurses affected INH adherence or frequency of adverse effects. METHODS: We retrospectively studied 3918 LTBI patients who received INH. At the discretion of the treating physician, 986 (25.2%) received house calls instead of clinic follow-up. Home-based follow-up included language translation, medication delivery, assessment of compliance with pill counts, monitoring for adverse effects, and active tracking of noncompliant patients. We assessed differences in patient characteristics, treatment completion, and reasons for treatment discontinuation between patients followed at home versus in the clinic. Multivariate analyses to address possible referral bias or confounding were performed using logistic regression. RESULTS: More patients followed with house calls completed INH treatment (90% home versus 73.2% clinic). This was the case across all subgroups of patients, including those with historically the lowest adherence: patients from correctional and rehabilitation facilities (77.8% home versus 46.9% clinic), postpartum women (86.4% home versus 55.6% clinic), and patients aged between 18 and 35 years (87% home versus 63.1% clinic). After adjusting for age, place of birth, referral category (TB contacts/skin test converters, correctional/rehabilitation patients, postpartum women, tuberculin positive patients from other screening), and prescribed INH regimen duration (9 versus 6 months), home-based follow-up of LTBI patients was a significant predictor of treatment completion (AOR 2.94, 95% CI: 2.33, 3.71). Patients followed at home were 21% more likely to complete therapy (ARR 1.21, p<0.001). Risk of adverse effects was similar between the two types of follow-up. CONCLUSION: Home-based follow-up of LTBI patients taking isoniazid was associated with improved treatment completion and no increase in adverse effects regardless of patient characteristics or prescribed duration of INH therapy.

Financial Incentives for COVID-19 Vaccines Among People Experiencing Homelessness.

INTRODUCTION: Novel strategies are needed to address barriers to COVID-19 vaccination among people experiencing homelessness (PEH), a population that faces increased COVID-19 risk. Although growing evidence suggests that financial incentives for vaccination are acceptable to PEH, their impact on uptake is unknown. This study aimed to assess whether offering $50 gift cards was associated with the uptake of the first doses of COVID-19 vaccine among PEH in Los Angeles County. METHODS: Vaccination clinics began on March 15, 2021; the financial incentive program was implemented from September 26, 2021 to April 30, 2022. Interrupted time-series analysis with quasi-Poisson regression was used to evaluate the level and slope change in the number of weekly first doses administered. Time-varying confounders included the weekly number of clinics and the weekly number of new cases. Demographic characteristics were compared for PEH vaccinated before and after the implementation of the incentive program using chi-square tests. RESULTS: Offering financial incentives was associated with the administration of 2.5 times (95% CI=1.8, 3.1) more first doses than would have been expected without the program. Level (-0.184, 95% CI= -1.166, -0.467) and slope change (0.042, 95% CI=0.031, 0.053) were observed. Individuals who were unsheltered, aged <55 years, and identified as Black or African American accounted for a higher percentage of those vaccinated during the post-intervention period than during the pre-intervention period. CONCLUSIONS: Financial incentives may be an effective tool for increasing vaccine uptake among PEH, but important ethical considerations must be made to avoid coercion of vulnerable populations.

Role of bacteria in oncogenesis.

Although scientific knowledge in viral oncology has exploded in the 20th century, the role of bacteria as mediators of oncogenesis has been less well elucidated. Understanding bacterial carcinogenesis has become increasingly important as a possible means of cancer prevention. This review summarizes clinical, epidemiological, and experimental evidence as well as possible mechanisms of bacterial induction of or protection from malignancy.

Race and Ethnicity and Sex Variation in COVID-19 Mortality Risks Among Adults Experiencing Homelessness in Los Angeles County, California.

Importance: Few studies have used precise age-specific data to construct age-standardized estimates of the relative risks (RRs) of COVID-19 mortality for people experiencing homelessness (PEH) vs the general population, and none to date has addressed race and ethnicity and sex variations in COVID-19 mortality among PEH with COVID-19 infection. Objective: To measure age-standardized mortality rate ratios for PEH vs the general population overall and by sex and race and ethnicity. Design, Setting, and Participants: In this cross-sectional study, crude and age-specific COVID-19 mortality rates per 100 000 people were calculated using 5-year age groups and standardized mortality ratios for PEH and the general population aged 25 years and older, assessing differences by race and ethnicity and sex, from January 1, 2020, to November 1, 2021. Mortality and population estimates came from COVID-19 mandatory case reporting conducted by the Los Angeles County Department of Public Health, the annual point-in-time homeless count, and the US Census. Main Outcomes and Measures: The main outcome was COVID-19 deaths sourced from clinician reports, death certificates, medical examiner reports, and vital records deaths. PEH status was determined using the US Department of Housing and Urban Development definitions for homelessness at the time of COVID-19 diagnosis or symptom onset. Results: The study population included 25 441 deaths among an estimated 6 382 402 general population individuals and 256 deaths among an estimated 52 015 PEH. The race and ethnicity of the PEH sample was as follows: 15 539 Black (29.9%), 18 057 Hispanic (34.7%), 14 871 female (28.6%), 37 007 male (71.3%), and 3380 aged 65 years or older (6.5%), compared with the estimated general population of 6 382 402, which was 591 003 Black (9.3%), 2 854 842 Hispanic (44.7%), 3 329 765 female (52.2%), 3 052 637 male (47.8%), and 1 190 979 aged 65 years or older (18.7%). Crude death rates were 0.49% for PEH and 0.40% for the general population, but PEH experienced age-specific COVID-19 mortality risk 2.35 (95% CI, 2.08-2.66) times higher than the general population. There was significant risk associated with PEH status compared with their counterparts in the general population for Black PEH (RR, 1.69; 95% CI, 1.31-2.18), Hispanic PEH (RR, 2.34; 95% CI, 1.96-2.79), White PEH (RR, 8.33; 95% CI, 6.37-10.88), female PEH (RR, 3.39; 95% CI, 2.56-4.48), and male PEH (RR, 1.74; 95% CI, 1.52-2.00). Conclusions and Relevance: This cross-sectional study of COVID-19 mortality among PEH with COVID-19 infection provides evidence suggesting excess risk of age-adjusted COVID-19 mortality among PEH compared with the general population. This study furthers understanding of the intersectional association between homelessness and race and ethnicity, as higher levels of mortality but narrower racial disparities among PEH than in the general population were observed.

Perceptions of Homeless Adults and Their Providers on Coping With the Impact of COVID-19 Pandemic on Mental Health, Substance Use, and Harm Reduction Services.

Adults experiencing homelessness experience a disproportionate burden of health disparities which has further exacerbated mental health, substance use, and coping during the COVID-19 pandemic. As limited data is available to understand the experience of adults experiencing homelessness and their health during this time, the purpose of this study was to explore how COVID-19 may have impacted their mental health, substance use, and ways of coping in this population. Using community-based participatory research, a community advisory board was established and remote individual interviews with 21 adults experiencing homelessness and 10 providers were conducted in Skid Row, Los Angeles. Using a qualitative, data analytic approach, the following major themes emerged: (1) Negative Impact of COVID-19 on Mental Health; (2) Negative Impact of COVID-19 on Limitation of Harm Reduction Services; and (3) Coping Strategies Utilized During the COVID-19 Pandemic. More research is needed to understand the impact of this pandemic on underserved communities.

COVID-19 Mortality Rates in Los Angeles County Among People Experiencing Homelessness, March 2020-February 2021.

OBJECTIVE: Understanding COVID-19-related mortality among the large population of people experiencing homelessness (PEH) in Los Angeles County (LA County) may inform public health policies to protect this vulnerable group. We investigated the impact of COVID-19 on PEH compared with the general population in LA County. METHODS: We calculated crude COVID-19 mortality rates per 100 000 population and mortality rates adjusted for age, race, and sex/gender among PEH and compared them with the general population in LA County from March 1, 2020, through February 28, 2021. RESULTS: Among adults aged ≥18 years, the crude mortality rate per 100 000 population among PEH was 20% higher than among the general LA County population (348.7 vs 287.6). After adjusting for age, the mortality rate among PEH was 570.7 per 100 000 population. PEH had nearly twice the risk of dying from COVID-19 as people in the general LA County population; PEH aged 18-29 years had almost 8 times the risk of dying compared with their peers in the general LA County population. PEH had a higher risk of mortality than the general population after adjusting for race (standardized mortality ratio [SMR] = 1.4; 95% CI, 1.2-1.6) and sex/gender (SMR = 1.3; 95% CI, 1.1-1.5). CONCLUSIONS: A higher risk of COVID-19-related death among PEH compared with the general population indicates the need for public health policies and interventions to protect this vulnerable group.

Cost-effectiveness of artificial intelligence monitoring for active tuberculosis treatment: A modeling study.

BACKGROUND: Tuberculosis (TB) incidence in Los Angeles County, California, USA (5.7 per 100,000) is significantly higher than the U.S. national average (2.9 per 100,000). Directly observed therapy (DOT) is the preferred strategy for active TB treatment but requires substantial resources. We partnered with the Los Angeles County Department of Public Health (LACDPH) to evaluate the cost-effectiveness of AiCure, an artificial intelligence (AI) platform that allows for automated treatment monitoring. METHODS: We used a Markov model to compare DOT versus AiCure for active TB treatment in LA County. Each cohort transitioned between health states at rates estimated using data from a pilot study for AiCure (N = 43) and comparable historical controls for DOT (N = 71). We estimated total costs (2017, USD) and quality-adjusted life years (QALYs) over a 16-month horizon to calculate the incremental cost-effectiveness ratio (ICER) and net monetary benefits (NMB) of AiCure. To assess robustness, we conducted deterministic (DSA) and probabilistic sensitivity analyses (PSA). RESULTS: For the average patient, AiCure was dominant over DOT. DOT treatment cost $4,894 and generated 1.03 QALYs over 16-months. AiCure treatment cost $2,668 for 1.05 QALYs. At willingness-to-pay threshold of $150K/QALY, incremental NMB per-patient under AiCure was $4,973. In univariate DSA, NMB were most sensitive to monthly doses and vocational nurse wage; however, AiCure remained dominant. In PSA, AiCure was dominant in 93.5% of 10,000 simulations (cost-effective in 96.4%). CONCLUSIONS: AiCure for treatment of active TB is cost-effective for patients in LA County, California. Increased use of AI platforms in other jurisdictions could facilitate the CDC's vision of TB elimination.

Mutation of Mycobacterium tuberculosis and Implications for Using Whole-Genome Sequencing for Investigating Recent Tuberculosis Transmission.

Tuberculosis (TB) control programs use whole-genome sequencing (WGS) of Mycobacterium tuberculosis (Mtb) for detecting and investigating TB case clusters. Existence of few genomic differences between Mtb isolates might indicate TB cases are the result of recent transmission. However, the variable and sometimes long duration of latent infection, combined with uncertainty in the Mtb mutation rate during latency, can complicate interpretation of WGS results. To estimate the association between infection duration and single nucleotide polymorphism (SNP) accumulation in the Mtb genome, we first analyzed pairwise SNP differences among TB cases from Los Angeles County, California, with strong epidemiologic links. We found that SNP distance alone was insufficient for concluding that cases are linked through recent transmission. Second, we describe a well-characterized cluster of TB cases in California to illustrate the role of genomic data in conclusions regarding recent transmission. Longer presumed latent periods were inconsistently associated with larger SNP differences. Our analyses suggest that WGS alone cannot be used to definitively determine that a case is attributable to recent transmission. Methods for integrating clinical, epidemiologic, and genomic data can guide conclusions regarding the likelihood of recent transmission, providing local public health practitioners with better tools for monitoring and investigating TB transmission.