Effects of environmental factors on severity and mortality of COVID-19

BackgroundMost respiratory viruses show pronounced seasonality, but for SARS-CoV-2 this still needs to be documented. MethodsWe examined the disease progression of COVID-19 in 6,914 patients admitted to hospitals in Europe and China. In addition, we evaluated progress of disease symptoms in 37,187 individuals reporting symptoms into the COVID Symptom Study application. FindingsMeta-analysis of the mortality risk in eight European hospitals estimated odds ratios per one day increase in the admission date to be 0.981 (0.973-0.988, p<0.001) and per increase in ambient temperature of one degree Celsius to be 0.854 (0.773-0.944, p=0.007). Statistically significant decreases of comparable magnitude in median hospital stay, probability of transfer to Intensive Care Unit and need for mechanical ventilation were also observed in most, but not all hospitals. The analysis of individually reported symptoms of 37,187 individuals in the UK also showed the decrease in symptom duration and disease severity with time. InterpretationSeverity of COVID-19 in Europe decreased significantly between March and May and the seasonality of COVID-19 is the most likely explanation. Mucosal barrier and mucociliary clearance can significantly decrease viral load and disease progression, and their inactivation by low relative humidity of indoor air might significantly contribute to severity of the disease.

Sterigmatocystin moderately induces oxidative stress in male Wistar rats after short-term oral treatment.

This study aimed to explore involvement of oxidative stress in sterigmatocystin (STC) toxicity in male Wistar rats. Animals were orally treated with a single STC dose (10, 20 and 40 mg/kg b.w.). Short-term treatment resulted in moderate oxidative stress determined by a significant increase of malondialdehyde (MDA; all STC doses) and catalase (CAT; 10 mg/kg b.w.) in plasma, a decrease of glutathione peroxidase (GPx; 20 and 40 mg/kg b.w.) in the liver, and increase of MDA and superoxide dismutase (SOD) in kidneys (all STC doses). Heat shock protein (Hsp27 and Hsp70) expression was determined by Western blotting in rat liver and kidneys. Hsp27 expression was downregulated by STC, particularly in the liver (40 mg/kg b.w.). The lowest STC dose elevated the expression of Hsp70 in both liver and kidneys, while an increase in STC doses restored Hsp70 expression to control. Alterations in expressions of Hsp27 and Hsp70 could be only partially associated with oxidative stress. STC provoked a significant DNA damage in both liver and kidneys (alkaline comet assay), but the liver was more affected by a broader spectrum of DNA lesions. Oxidative DNA damage (hOGG1-modified comet assay) contribute to the overall mechanism of STC-induced DNA damage in both organs, but kidneys in general seem to be more susceptible to oxidative stress upon short-term exposure to sublethal doses of STC.