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The role that environmental factors can play in preventing and controlling the Covid-19 epidemic was explored and compared to that of influenza. Papers cited by the U.S. National Academy of Sciences were discussed, which indicate that temperature and humidity in the environment can influence the intensity of the spread of the disease. The fact that influenza viruses and coronaviruses appeared seasonally, prevailing in the winter and declining in the summer, was illustrated. It was discussed that ultraviolet light in the environment can contribute to the control of the spread of the virus. A study was cited to suggest that particulate matter contributes to increased infection mortality, and that it increases in summer in some regions, countering the health effects of humidity and temperature. Data generated by online electronic tools was compared with surveillance reports generated by the U.S. Centers for Disease Control and Prevention. The epidemic began stronger in northern hemisphere countries during the northern winter. (Evidence that the epidemic intensified during the southern winter is not disputed.) The incidence declined in the northern hemisphere during the summer, except for the U.S., where cases doubled. Evidence suggests that the high degree of SARS-CoV-2 infection counteracts the role that environmental factors may play in Covid-19 control.

Background: In the scientific literature, the impacts of plateletpheresis on leukogram parameters are not clear, with a high divergence in the studies that have evaluated changes in leukocytes. The objective of this paper was to meta-analyze the effect of plateletpheresis on the leukocyte count, based on studies published between 1980-2018., Methods: Systematic review with meta-analysis of random effects for the difference of means. The phases of the PRISMA guide were applied with 132 search strategies in Pubmed, Scielo, Science direct and Scopus. Reproducibility and evaluation of methodological quality were guaranteed. Heterogeneity was evaluated with Galbraith and Dersimonian and Laird's, publication bias with Funnel Plot and Begg; sensitivity analysis, accumulated meta-analysis and Forest Plot were carried out., Results: Nineteen studies were included with 2,358 donors, mostly from India, United States, Turkey, Germany and Austria. A mean difference of -0,80 x109⁄L (IC95%= -1,96; 0,36x109⁄L) between the predonation value and the value immediately after donation was founded; no publication bias was found and the conclusion presented good sensitivity since it does not vary with the elimination of studies in successive phases., Conclusions: The donation of platelets by apheresis does not affect the leukocyte count in the donors, in the last century there were reports of reductions in this parameter, explained by the blood loss in the cases used for the procedure and by effects produced in the blood cells by the biomaterials; however, at present the high safety of plateletpheresis for the white blood cell count is evidenced.