A question central to the Covid-19 pandemic is why the Covid-19 mortality rate varies so greatly across countries. This study aims to investigate factors associated with crosscountry variation in Covid-19 mortality. Covid-19 mortality rate was calculated as number of deaths per 100 Covid-19 cases. To identify factors associated with Covid-19 mortality rate, linear regressions were applied to a cross-sectional dataset comprising 169 countries. We retrieved data from the Worldometer website, the Worldwide Governance Indicators, World Development Indicators, and Logistics Performance Indicators databases. Covid-19 mortality rate was negatively associated with Covid-19 test number per 100 people (RR = 0.92, P = 0.001), government effectiveness score (RR = 0.96, P = 0.017), and number of hospital beds (RR = 0.85, P < 0.001). Covid-19 mortality rate was positively associated with proportion of population aged 65 or older (RR = 1.12, P < 0.001) and transport infrastructure quality score (RR = 1.08, P = 0.002). Furthermore, the negative association between Covid-19 mortality and test number was stronger among low-income countries and countries with lower government effectiveness scores, younger populations and fewer hospital beds. Predicted mortality rates were highly associated with observed mortality rates (r = 0.77; P < 0.001). Increasing Covid-19 testing, improving government effectiveness and increasing hospital beds may have the potential to attenuate Covid-19 mortality. Since the first report of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing coronavirus disease 2019 (Covid-19) 1,2 , more than 8.7 million people have been infected and more than 460 thousand have died worldwide as of June 20, 2020. The highly contagious Covid-19 has led to large numbers of infections, health care system overload, and lockdowns in many countries 3-5. A question central to the Covid-19 pandemic is why the Covid-19 mortality rate varies so greatly across countries, from over 16% in France and Belgium to less than 0.1% in Singapore and Qatar. Such wide variation implies that there are factors other than patient characteristics that determine Covid-19 mortality, such as government response. Patient-level studies have shown that Covid-19 mortality can be explained by age, obesity, and underlying diseases, such as hypertension, diabetes, and coronary heart disease, etc. 6-8 , as well as clinical symptoms, complications, hospital care, previous immunity and virus mutations 9,10. These findings help health professionals to identify high-risk patients. However, this evidence alone may not be sufficient to support effective policies for reducing Covid-19 mortality. This gap in Covid-19 research has been addressed by several studies. Some scholars have discussed the effectiveness of governments' policies, such as quarantine or lockdown, in slowing the spread of Covid-19 3,11. Others have suggested that projecting hospital utilization during the Covid-19 outbreak is necessary to assure

Obesity is worldwide epidemic given its rapid growth in global prevalence. Among the risk factors contributing to obesity, human gut microbiome recently emerges with unprecedented intimacy in host metabolism and inflammation. With the advances in sequencing technology, more and more detailed understandings towards the intricate relationships linking gut microbiome and obesity have been continuously disclosed. Herein, we review studies resolving associations between gut microbiome and obesity, and then mechanistic studies tackling the roles played by gut microbes in obesogenic physiology.

Objectives The intestinal microbiota has been known to involve in obesity and host immune response. We aimed to investigate the intestinal microbiota and potential genetic function in relation to clinical presentation in psoriasis patients. Methods Faecal microbiota and predicted genetic function inferred from high‐throughput 16S ribosomal RNA sequencing were analysed between psoriasis (n = 32) and age‐, gender‐ and body mass index (BMI)‐matched non‐psoriasis subjects (n = 64), from a referral medical centre. The correlation between altered microbiota and disease activity, arthritis and systemic anti‐psoriatic drugs was also investigated. Results We observed a distinct faecal microbial community structure in psoriasis patients, with an increased abundance of phylum Firmicutes and decreased abundance of phylum Bacteroidetes, across different subgroup of subjects. Ruminococcus and Megasphaera, of the phylum Firmicutes, were the top‐two genera of discriminant abundance in psoriasis. A number of functional genes and metabolic pathways involving bacterial chemotaxis and carbohydrate transport were predicted over‐represented, whereas genes related to cobalamin and iron transport were predicted under‐represented in faecal microbiota of psoriasis patients. Conclusions The distinct faecal microbial composition in psoriasis might be associated with altered transport of carbohydrate, cobalamin and iron, as well as chemotaxis.

Diet and exercise are conventional methods for controlling body weight and are linked to alterations in gut microbiota. However, the associations of diet, exercise, and gut microbiota in the control of obesity remain largely unknown. In the present study, using 16S rRNA amplicon sequencing and fecal microbiota transplantation (FMT), normal fat diet (NFD), exercise and their combination resulted in improved metabolic profiles in comparison to sedentary lifestyle with high fat diet (HFD). Moreover, diet exerted more influence than exercise in shaping the gut microbiota. HFD-fed mice receiving FMT from NFD-exercised donors not only showed remarkably reduced food efficacy, but also mitigated metabolic profiles (p < 0.05). The transmissible beneficial effects of FMT were associated with bacterial genera Helicobacter, Odoribacter and AF12 and overrepresentation of oxidative phosphorylation and glycolysis genes. Our findings demonstrate that the beneficial effects of diet and exercise are transmissible via FMT, suggesting a potential therapeutic treatment for obesity.

Subtotal gastrectomy (i.e., partial removal of the stomach), a surgical treatment for early-stage distal gastric cancer, is usually accompanied by highly selective vagotomy and Billroth II reconstruction, leading to dramatic changes in the gastric environment. Based on accumulating evidence of a strong link between human gut microbiota and host health, a 2-year follow-up study was conducted to characterize the effects of subtotal gastrectomy. Gastric microbiota and predicted gene functions inferred from 16S rRNA gene sequencing were analyzed before and after surgery. The results demonstrated that gastric microbiota is significantly more diverse after surgery. Ralstonia and Helicobacter were the top two genera of discriminant abundance in the cancerous stomach before surgery, while Streptococcus and Prevotella were the two most abundant genera after tumor excision. Furthermore, N-nitrosation genes were prevalent before surgery, whereas bile salt hydrolase, NO and N2O reductase were prevalent afterward. To our knowledge, this is the first report to document changes in gastric microbiota before and after surgical treatment of stomach cancer.

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Endozoicomonas bacteria are commonly regarded as having a potentially symbiotic relationship with their coral hosts. However, their diversity and phylogeny in samples collected from various sources remain unclear. Therefore, we designed an Endozoicomonas-specific primer paired with a bacterial universal primer to detect the 16S ribosomal RNA (rRNA) genes of this taxon and conducted an in-depth investigation of the Endozoicomonas community structure in reef-building corals. The primer had high specificity in the V3–V4 region (95.6%) and its sensitivity was high, particularly when Endozoicomonas was rare in samples (e.g., in seawater, which had a higher alpha diversity of Endozoicomonas than corals). In coral samples, predominant V3–V4 ribotypes had greater divergence than predominant V1–V2 ribotypes, and were grouped into at least 9 novel clades in a phylogenetic tree, indicating Endozoicomonas had high phylogenetic diversity. Divergence within this genus was potentially higher than that among 7 outgroup genera based on the phylogenetic distances of partial 16S rDNA sequences, suggesting that the taxonomy of this genus needs to be revised. In conclusion, dominant Endozoicomonas populations had variable phylogenies; furthermore, the newly designed primers may be useful molecular tools for the reliable detection of the Endozoicomonas community in marine environments.

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