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Promoting health equity is a fundamental public health objective, yet health disparities remain largely overlooked in studies of vectorborne diseases, especially those transmitted by ticks. We sought to identify health disparities associated with Lyme disease and human monocytic ehrlichiosis, two of the most pervasive tickborne diseases within the United States. We used general linear mixed models to measure associations between county-level disease incidence and six variables representing racial/ethnic and socioeconomic characteristics of counties (percent white non-Hispanic; percent with a bachelors degree or higher; percent living below the poverty line; percent unemployed; percent of housing units vacant; per capita number of property crimes). Two ecological variables important to tick demography (percent forest cover; density of white-tailed deer) were included in secondary analyses to contextualize findings. Analyses included data from 2,695 counties in 37 states and the District of Columbia during 2007-2013. Each of the six variables was significantly associated with the incidence of one or both diseases, but the direction and magnitude of associations varied by disease. Results suggested that the incidence of Lyme disease was highest in counties with relatively higher proportions of white and more educated persons and lower poverty and crime rates; the incidence of human monocytic ehrlichiosis was highest in counties with relatively higher proportions of white and less educated persons, higher unemployment rates and lower crime rates. The percentage of housing units vacant was a strong positive predictor for both diseases with a magnitude of association comparable to those between incidence and the ecological variables. Our findings indicate that racial/ethnic and socioeconomic disparities in disease incidence appear to be epidemiologically important features of Lyme disease and human monocytic ehrlichiosis in the United States. Steps to mitigate encroachment of wild flora and fauna into areas with vacant housing might be warranted to reduce disease risk.

Because disease resistance is a hallmark signature of pathogen-mediated selection pressure on hosts, studies of resistance structure (the spatial distribution of disease resistance genes among conspecific host populations) can provide valuable insights into the influence of pathogens on host evolution and spatial variation in the magnitude of their effects. To date few studies of wild plant–pathogen interactions have characterized resistance structure by sampling across the host's biogeographic range, and only a handful have paired such investigations with studies of disease levels under natural conditions. I used a greenhouse cross-inoculation experiment to characterize genetic resistance of 16 populations of California dwarf flax (Hesperolinon californicum) to attack by multiple samples of the rust fungus Melampsora lini. I documented a latitudinal cline in resistance structure, manifest across the host's biogeographic range, which mirrored almost identically a cline in infection prevalence documented through field surveys of disease in study populations. These results provide empirical evidence for clinal patterns of antagonistic selection pressure, demonstrate that such patterns can be manifest across broad biogeographic scales, and suggest that rates of disease prevalence in wild plant populations may be tightly linked to the distribution of host resistance genes. Tests for local adaptation of the fungus revealed evidence of the phenomenon (significantly greater infection in sympatric plant–fungal pairings) as well as the potential for substantial bias to be introduced into statistical analyses by spatial patterns of host resistance structure.

Objectives. We quantified the relationship between gonorrheal infection rates in California and a measure of poverty status and investigated how this relationship and the spatial dispersion of cases varied among the 4 dominant racial/ethnic groups in the state. Methods. We geocoded gonorrhea cases reported in California between 2004 and 2006, and estimated the poverty status of each case by using the percentage of residents living below poverty in the census tract of residence. We calculated infection rates for African American, Asian, Hispanic, and White cases in each of 4 poverty strata. We mapped cases to visualize the patterns of spatial dispersion associated with each race/ethnicity–poverty combination. Results. There was a strong positive relationship between poverty and infection, but racial/ethnic disparities in infection, driven by a disproportionate level of gonorrhea among African Americans, eclipsed this differential. The degree of spatial aggregation varied substantially among groups and was especially pronounced for African Americans with gonorrhea in the highest poverty category. Conclusions. Prevention efforts should target low-income neighborhood “hot spots” to reach the largest numbers of cases, particularly among African Americans.

Objectives. To examine impacts of racial and ethnic disaggregation on the characterization of tuberculosis (TB) epidemiology among American Indian and Alaska Native (AI/AN) persons in the United States. Methods. Using data reported to the National Tuberculosis Surveillance System during 2001 to 2020, we compared annual age-adjusted TB incidence and the frequency of TB risk factors among 3 AI/AN analytic groups: non-Hispanic AI/AN alone persons, multiracial/Hispanic AI/AN persons, and all AI/AN persons (aggregate of the first 2 groups). Results. During 2009 to 2020, annual TB incidence (cases per 100 000 persons) among non-Hispanic AI/AN alone persons (range = 3.87–8.56) was on average 1.9 times higher than among all AI/AN persons (range = 1.89–4.70). Compared with non-Hispanic AI/AN alone patients with TB, multiracial/Hispanic AI/AN patients were significantly more likely to be HIV positive (prevalence ratio [PR] = 2.05) and to have been diagnosed while a resident of a correctional facility (PR = 1.71), and significantly less likely to have experienced homelessness (PR = 0.53) or died during TB treatment (PR = 0.47). Conclusions. Racial and ethnic disaggregation revealed significant differences in TB epidemiology among AI/AN analytic groups. Exclusion of multiracial/Hispanic AI/AN persons from AI/AN analytic groups can substantively affect estimates of racial and ethnic health disparities. ( Am J Public Health. 2024;114(2):226–236. https://doi.org/10.2105/AJPH.2023.307498 )

Background. Human infection by orthopoxviruses is being reported with increasing frequency, attributed in part to the cessation of smallpox vaccination and concomitant waning of population-level immunity. In July 2015, a female resident of interior Alaska presented to an urgent care clinic with a dermal lesion consistent with poxvirus infection. Laboratory testing of a virus isolated from the lesion confirmed infection by an Orthopoxvirus. Methods. The virus isolate was characterized by using electron microscopy and nucleic acid sequencing. An epidemiologic investigation that included patient interviews, contact tracing, and serum testing, as well as environmental and small-mammal sampling, was conducted to identify the infection source and possible additional cases. Results. Neither signs of active infection nor evidence of recent prior infection were observed in any of the 4 patient contacts identified. The patient's infection source was not definitively identified. Potential routes of exposure included imported fomites from Azerbaijan via the patient's cohabiting partner or wild small mammals in or around the patient's residence. Phylogenetic analyses demonstrated that the virus represents a distinct and previously undescribed genetic lineage of Orthopoxvirus, which is most closely related to the Old World orthopoxviruses. Conclusions. Investigation findings point to infection of the patient after exposure in or near Fairbanks. This conclusion raises questions about the geographic origins (Old World vs North American) of the genus Orthopoxvirus. Clinicians should remain vigilant for signs of poxvirus infection and alert public health officials when cases are suspected.

Abiotically extreme environments are often associated with physiologically stressful conditions, small, low-density populations, and depauperate flora and fauna relative to more benign settings. A possible consequence of this may be that organisms that occupy these stressful habitats receive fitness benefits associated with reductions in the frequency and/or intensity of antagonistic species interactions. I investigated a particular form of this effect, formalized as the \"pathogen refuge hypothesis,\" through a study of 13 species of wild flax that grow on stressful serpentine soils and are often infected by a pathogenic fungal rust. The host species vary in the degree of their serpentine association: some specialize on extreme serpentine soils, while others are generalists that occur on soils with a wide range of serpentine influence. Phylogenetically explicit analyses of soil chemistry and field-measured disease levels indicated that rust disease was significantly less frequent and severe in flax populations growing in more stressful, low-calcium serpentine soils. These findings may help to explain the persistence of extremophile species in habitats where stressful physical conditions often impose strong autecological fitness costs on associated organisms. Ancestral state reconstruction of serpentine soil tolerance (approximated using soil calcium concentrations) suggested that the ability to tolerate extreme serpentine soils may have evolved multiple times within the focal genus.

Background Populations of indigenous persons are frequently associated with pronounced disparities in rates of tuberculosis (TB) disease compared to co-occurring nonindigenous populations. Methods Using data from the National Tuberculosis Surveillance System on TB cases in U.S.-born patients reported in the United States during 2009–2019, we calculated incidence rate ratios and risk ratios for TB risk factors to compare cases in American Indian or Alaska Native (AIAN) and Native Hawaiian or other Pacific Islander (NHPI) TB patients to cases in White TB patients. Results Annual TB incidence rates among AIAN and NHPI TB patients were on average ≥10 times higher than among White TB patients. Compared to White TB patients, AIAN and NHPI TB patients were 1.91 (95% confidence interval (CI): 1.35–2.71) and 3.39 (CI: 1.44–5.74) times more likely to have renal disease or failure, 1.33 (CI: 1.16–1.53) and 1.63 (CI: 1.20–2.20) times more likely to have diabetes mellitus, and 0.66 (CI: 0.44–0.99) and 0.19 (CI: 0–0.59) times less likely to be HIV positive, respectively. AIAN TB patients were 1.84 (CI: 1.69–2.00) and 1.48 (CI: 1.27–1.71) times more likely to report using excess alcohol and experiencing homelessness, respectively. Conclusion TB among U.S. indigenous persons is associated with persistent and concerning health disparities.

Spatial variation in the frequency and outcome of interspecific interactions is thought to play a central role in shaping geographic patterns of biodiversity. Previous empirical studies and modeling exercises suggest that negative species interactions should occur with greater frequency and intensity in high-quality/low-stress environments. I tested this hypothesis through a four-year epidemiological study of interactions between the plant Hesperolinon californicum and the pathogenic rust fungus Melampsora lini. By virtue of its association with serpentine soils, H. californicum is exposed to edaphic conditions that are stressful to most plants. Notable among these is the low availability of calcium, an element that plays critically important roles in the immune responses of plants to attacking pathogens. As a serpentine generalist, however, H. californicum grows in soils with a wide range of calcium concentrations, and this should lead to differences in the frequency and/or severity of rust infection among host populations. I investigated geographic variation in disease pressure by conducting annual surveys in 16 populations spanning the host's distribution and representing a range of soil calcium concentrations. Results indicated that plants growing in more stressful low-calcium soils experienced higher rates of rust infection, suggesting that soil calcium may modulate host susceptibility in a manner opposite to that predicted by the a priori hypothesis. Epidemiological surveys further revealed a latitudinal cline in disease prevalence, with high infection rates in northern host populations decreasing gradually toward the south. Studies of the fitness effects of disease demonstrated that rust infection caused significant reductions in host survival and fecundity, and there was evidence of a demographic feedback between infection prevalence and host density across survey years.

PREMISE OF THE STUDY: Hesperolinon (western flax; Linaceae) is endemic to the western United States, where it is notable for its high and geographically concentrated species diversity on serpentine-derived soils and for its use as a model system in disease ecology. We used a phylogenetic framework to test a long-standing hypothesis that Hesperolinon is a neoendemic radiation. METHODS: Five plastid and two ribosomal nuclear DNA gene regions were sampled from 105 populations of Hesperolinon, including all 13 recently recognized species across their known ranges. We used these data to generate population-level phylogenies of Hesperolinon. We also generated a robustly sampled chronogram of Linaceae using an eight-gene, 100-taxon supermatrix calibrated using fossil Linum pollen and a published chronogram of Malpighiales. KEY RESULTS: Most diversification in Hesperolinon has taken place in the past 1-2 million yr, much more recently than previous estimates. Only the earliestdiverging species, H. drymarioides, was resolved as a clade. Denser taxon and gene sampling generally support previously proposed relationships within Linaceae, but with more recent diversification of key clades. CONCLUSIONS: Hesperolinon is an excellent example of edaphic neoendemism, in support of Raven and Axelrod's hypothesis for the genus. Dense population-level sampling reveals a complex of incipient species, with clades poorly aligned with traditional morphological circumscriptions, likely due in part to continued gene flow. The diversification of Linaceae is more recent than previously estimated, and other recent radiations (e.g., Hugonia) warrant further study.

Rapid changes in climate and land use and the resulting shifts in species distributions and ecosystem functions have motivated the development of the National Ecological Observatory Network (NEON). Integrating across spatial scales from ground sampling to remote sensing, NEON will provide data for users to address ecological responses to changes in climate, land use, and species invasion across the United States for at least 30 years. Although NEON remote sensing and tower sensor elements are relatively well known, the biological measurements are not. This manuscript describes NEON terrestrial sampling, which targets organisms across a range of generation and turnover times, and a hierarchy of measurable biological states. Measurements encompass species diversity, abundance, phenology, demography, infectious disease, ecohydrology, and biogeochemistry. The continental-scale sampling requires collection of comparable and calibrated data using transparent methods. Data will be publicly available in a variety of formats and suitable for integration with other long-term efforts. NEON will provide users with the data necessary to address large-scale questions, challenge current ecological paradigms, and forecast ecological change.