Do racial and ethnic disparities in following stay-at-home orders influence COVID-19 health outcomes? A mediation analysis approach.

Racial/ethnic disparities are among the top-selective underlying determinants associated with the disproportional impact of the COVID-19 pandemic on human mobility and health outcomes. This study jointly examined county-level racial/ethnic differences in compliance with stay-at-home orders and COVID-19 health outcomes during 2020, leveraging two-year geo-tracking data of mobile devices across ~4.4 million point-of-interests (POIs) in the contiguous United States. Through a set of structural equation modeling, this study quantified how racial/ethnic differences in following stay-at-home orders could mediate COVID-19 health outcomes, controlling for state effects, socioeconomics, demographics, occupation, and partisanship. Results showed that counties with higher Asian populations decreased most in their travel, both in terms of reducing their overall POIs' visiting and increasing their staying home percentage. Moreover, counties with higher White populations experienced the lowest infection rate, while counties with higher African American populations presented the highest case-fatality ratio. Additionally, control variables, particularly partisanship, median household income, percentage of elders, and urbanization, significantly accounted for the county differences in human mobility and COVID-19 health outcomes. Mediation analyses further revealed that human mobility only statistically influenced infection rate but not case-fatality ratio, and such mediation effects varied substantially among racial/ethnic compositions. Last, robustness check of racial gradient at census block group level documented consistent associations but greater magnitude. Taken together, these findings suggest that US residents' responses to COVID-19 are subject to an entrenched and consequential racial/ethnic divide.

Quantifying human mobility behaviour changes during the COVID-19 outbreak in the United States.

Since the first case of the novel coronavirus disease (COVID-19) was confirmed in Wuhan, China, social distancing has been promoted worldwide, including in the United States, as a major community mitigation strategy. However, our understanding remains limited in how people would react to such control measures, as well as how people would resume their normal behaviours when those orders were relaxed. We utilize an integrated dataset of real-time mobile device location data involving 100 million devices in the contiguous United States (plus Alaska and Hawaii) from February 2, 2020 to May 30, 2020. Built upon the common human mobility metrics, we construct a Social Distancing Index (SDI) to evaluate people's mobility pattern changes along with the spread of COVID-19 at different geographic levels. We find that both government orders and local outbreak severity significantly contribute to the strength of social distancing. As people tend to practice less social distancing immediately after they observe a sign of local mitigation, we identify several states and counties with higher risks of continuous community transmission and a second outbreak. Our proposed index could help policymakers and researchers monitor people's real-time mobility behaviours, understand the influence of government orders, and evaluate the risk of local outbreaks.

Wnt-activated olfactory ensheathing cells stimulate neural stem cell proliferation and neuronal differentiation.

Olfactory ensheathing cells (OECs) are special glial cells localized in olfactory system which secrete large number of neurotrophic factors and promote the migration and survival of neurons. Canonical Wnt/ß-catenin signaling is activated in OECs during development and facilitates the growth and regeneration of axons. In the present study, we investigated the effects of Wnt-activated OECs on the proliferation and differentiation of neural stem cells (NSCs) in vitro. Primary neonatal mouse OECs were cultured and identified by immunostaining of P75 and GFAP. Wnt activation was achieved by lentivirus transfection of dominant-active-ß-catenin (EbC) and examined by immunostaining of PY489. The conditioned medium (CM) of Wnt-activated OECs (wOECs-CM) and control OECs (cOECs-CM) was used to stimulate NSCs. In proliferation assay, wOECs-CM could increase the percentage of Ki67/Sox2 double positive cells. Under differentiation condition, wOECs-CM could maintain the expression of Nestin and promote the differentiation of NSCs into Tuj1-positive neurons. Taken together, our data revealed that wOECs stimulates the proliferation and differentiation of NSCs in a secretory manner, indicating that combined transplantation of wOECs and NSCs may be beneficial for regeneration.