Will Coronavirus Pandemic Diminish by Summer?

Containment measures limit environmental effects on COVID-19 early outbreak dynamics

“…The best model including humidity also showed slightly larger growth rates in countries with greater health expenditure (Table S5), possibly because of more efficient early reporting and/or faster diagnosis of Covid-19 cases. Results were highly consistent if we calculated growth rates after minimum thresholds of 25 or 100 cases (r 25 and r 100 , 15 respectively) instead of 50 (Tables S3 and S5). Human population density and air pollution showed very limited relative importance values (always < 0.50; Table S1), suggesting that they play a relatively minor role in determining Covid-19 growth rates, at least at the coarse spatial scale of this study.…”

“…1A-C). The observed daily growth rate after reaching 50 cases (r 50 ) was on average 0.22 [95% CI 0.19-0.24], 15 and ranged from 0.01 (Kuwait) to 0.55 (Denmark). The highest growth rates were observed in temperate regions of the Northern Hemisphere, although fast growth also occurred in some warm climates, as observed in Brazil and the Philippines, suggesting that no area is exempt from risk Climate variables were the most important predictors of Covid-19 growth rate (Table S1).…”

“…The clear relationship between COVID-19 growth rate and climate suggests that seasonal climatic variation may affect the spatial spread and severity of COVID-19 outbreaks (14), as observed for other virus-caused diseases (3,6). We thus displayed potential seasonal changes in 5 Covid-19 growth rates by projecting our best model of r 50 in relation to temperature under the average temperature conditions of the current (March) and next (June and September) months 15 SARS-CoV2 shows a substantial rate of undocumented infections that could facilitate the spread of the disease (21). This may affect our analyses, which are based on the number of confirmed positive cases (8,9).…”

“…Temperature and humidity strongly impact the variation of the growth rate of Covid-19 cases across the globe. 15…”

“…Some countries have been experiencing limited growth and spread of Covid-19 cases, while others are suffering widespread community transmission and nearly exponential growth of infections (8). Understanding the drivers of early growth rates is pivotal to predict progresses of disease outbreaks in the absence of containment measures (9, 10), yet no study has so far assessed the role of environmental variation in the worldwide growth of 15 Covid-19 cases. Given the impact of environmental conditions on the transmission of many pathogens, we tested the hypothesis that the severity of Covid-19 outbreaks across the globe is affected by spatial variation of key environmental factors, such as temperature, air humidity (5,(11)(12)(13)(14)(15), and pollution [fine particulate matter (16); see methods].…”