In the version of this caption initially published, the cover artwork was credited to Erin Dewalt, based on imagery from the author, rather than stating that it was created by Michael B. Battles and the design was by Erin Dewalt. The error has been corrected in the HTML and PDF versions of the caption. ERRATUM In the version of this article initially published, the genus name 'Mycoplasma' was incorrectly used in place of the correct 'Mycobacterium'. The error has been corrected in the HTML and PDF versions of the article. ERRATUM npg

Background: COVID-19 is a highly infectious respiratory disease. No therapeutics have yet been proven effective for treating severe COVID-19. Objectives: To determine whether human umbilical cord mesenchymal stem cell infusion may be effective and safe for the treatment of severe COVID-19. Methods: Patients with severe COVID-19 were randomly divided into 2 groups: the standard treatment group and the standard treatment plus hUC-MSC infusion group. The incidence of progression from severe to critical illness, 28-day mortality, clinical symptom improvement, time to clinical symptom improvement, hematologic indicators including C-reactive protein, lymphocyte number, and interleukin 6, and imaging changes were observed and compared between the two groups. Measurements and main results: The incidence of progression from severe to critical illness and the 28-day mortality rate were 0 in the hUC-MSC treatment group, while 4 patients in the control group deteriorated to critical condition and received invasive ventilation; 3 of them died, and the 28-day mortality rate was 10.34%. In the hUC-MSC treatment group, the time to clinical improvement was shorter than that in the control group. Clinical symptoms of weakness and fatigue, shortness of breath, and low oxygen saturation obviously improved beginning on the third day of stem cell infusion and reached a significant difference on day 7. CRP and IL-6 levels were significantly lower from day 3 of infusion, the time for the lymphocyte count to return to the normal range was significantly faster, and lung inflammation absorption was significantly shorter on CT imaging in the hUC-MSC group than in the control group. Conclusions: Intravenous transplantation of hUC-MSCs is a safe and effective method that can be considered a salvage and priority treatment option for severe COVID-19.

Cholera remains an important global cause of morbidity and mortality, capable of causing periodic epidemic disease. Beginning in August 2008, a major cholera epidemic occurred in Zimbabwe, with 98,585 reported cases and 4,287 deaths. The dynamics of such outbreaks, particularly in nonestuarine regions, are not well understood. We explored the utility of mathematical models in understanding transmission dynamics of cholera and in assessing the magnitude of interventions necessary to control epidemic disease. Weekly data on reported cholera cases were obtained from the Zimbabwe Ministry of Health and Child Welfare (MoHCW) for the period from November 13, 2008 to July 31, 2009. A mathematical model was formulated and fitted to cumulative cholera cases to estimate the basic reproductive numbers R 0 and the partial reproductive numbers from all 10 provinces for the 2008–2009 Zimbabwe cholera epidemic. Estimated basic reproductive numbers were highly heterogeneous, ranging from a low value of just above unity to 2.72. Partial reproductive numbers were also highly heterogeneous, suggesting that the transmission routes varied by province; human-to-human transmission accounted for 41–95% of all transmission. Our models suggest that the underlying patterns of cholera transmission varied widely from province to province, with a corresponding variation in the amenability of outbreaks in different provinces to control measures such as immunization. These data underscore the heterogeneity of cholera transmission dynamics, potentially linked to differences in environment, socio-economic conditions, and cultural practices. The lack of traditional estuarine reservoirs combined with these estimates of R 0 suggest that mass vaccination against cholera deployed strategically in Zimbabwe and surrounding regions could prevent future cholera epidemics and eventually eliminate cholera from the region.

Obesity is a severe health problem in children, afflicting several organ systems including bone. However, the role of obesity on bone homeostasis and bone cell function in children has not been studied in detail. Here we used young mice fed a high-fat diet (HFD) to model childhood obesity and investigate the effect of HFD on the phenotype of cells within the bone marrow environment. Five-week-old male mice were fed a HFD for 3, 6, and 12 weeks. Decreased bone volume was detected after 3 weeks of HFD treatment. After 6 and 12 weeks, HFD-exposed mice had less bone mass and increased osteoclast numbers. Bone marrow cells, but not spleen cells, from HFD-fed mice had increased osteoclast precursor frequency, elevated osteoclast formation and bone resorption activity, as well as increased expression of osteoclastogenic regulators including RANKL, TNF, and PPAR-gamma. Bone formation rate and osteoblast and adipocyte numbers were also increased in HFD-fed mice. Isolated bone marrow cells also had a corresponding elevation in the expression of positive regulators of osteoblast and adipocyte differentiation. Our findings indicate that in juvenile mice, HFD-induced bone loss is mainly due to increased osteoclast bone resorption by affecting the bone marrow microenvironment. Thus, targeting osteoclast formation may present a new therapeutic approach for bone complications in obese children. 5Co-corresponding author: Xing, Lianping,