SarsCoV2 infection has a seasonal pattern: cold and humidity affect the transmission of the virus, just like with the flu. Air hygiene in closed environments therefore becomes fundamental, as emerges from the quantitative analysis of the Covid-19 waves that have occurred so far, published in the magazine Nature Computational Science from the Barcelona Institute for Global Health.
“The question of whether Covid-19 is a seasonal disease is increasingly central”, comments Xavier Rodó, coordinator of the study. To understand this, the researchers have analyzed the association with temperature and humidity in the initial phase of the spread of the virus in 162 countries on 5 continents, before the restrictions on human behavior were adopted. A negative relationship has thus emerged in the transmission rate (R0), temperature and humidity on a global scale: the higher transmission rates are associated with lower temperatures and humidity.
By analyzing the temporal and geographical evolution of the link between climate and disease, the researchers have found a negative association between disease (number of cases) and climate (temperature and humidity), with compatible trends in the three pandemic waves at different latitudes: world, country and regional, with highly affected regions (such as Lombardy, Thuringia and Catalonia) or even at city level (Barcelona). The first epidemic wave subsided with rising temperatures and humidity, while the second has grown with the drop in humidity and temperatures. A pattern that was interrupted in the summer months on all continents.
By adapting the model to the countries of the southern hemisphere, where the virus arrived later, the same correlation was observed. The effects of the climate are more evident with temperatures between 12 ° and 18 ° and a humidity level between 4 and 12 grams per cubic meter, even if these are indicative figures, the authors warn. “Our results – adds Rodó – support the idea that Covid infection is seasonal, linked to base temperatures, like influenza and the other more benign coronaviruses in circulation”.