Role of meteorological factors in the transmission of SARS-CoV-2 in the United States

Abstract

Improved understanding of the effects of meteorological conditions on the transmission of SARS-CoV-2, the causative agent for COVID-19 disease, is needed. Here, we estimate the relationship between air temperature, specific humidity, and ultraviolet radiation and SARS-CoV-2 transmission in 2669 U.S. counties with abundant reported cases from March 15 to December 31, 2020. Specifically, we quantify the associations of daily mean temperature, specific humidity, and ultraviolet radiation with daily estimates of the SARS-CoV-2 reproduction number (Rt) and calculate the fraction of Rt attributable to these meteorological conditions. Lower air temperature (within the 20–40 °C range), lower specific humidity, and lower ultraviolet radiation were significantly associated with increased Rt. The fraction of Rt attributable to temperature, specific humidity, and ultraviolet radiation were 3.73% (95% empirical confidence interval [eCI]: 3.66–3.76%), 9.35% (95% eCI: 9.27–9.39%), and 4.44% (95% eCI: 4.38–4.47%), respectively. In total, 17.5% of Rt was attributable to meteorological factors. The fractions attributable to meteorological factors generally were higher in northern counties than in southern counties. Our findings indicate that cold and dry weather and low levels of ultraviolet radiation are moderately associated with increased SARS-CoV-2 transmissibility, with humidity playing the largest role.

COVID-19 pandemic dynamics in India, the SARS-CoV-2 Delta variant, and implications for vaccination

“…While the model used to estimate COVID-19 seasonal trends was developed for influenza; 14 studies have shown a similar impact of humidity and temperature on SARS-CoV-2 transmission as observed for influenza. 15,16 In addition, our previous estimates for Beta and South Africa using the same model appear to have been borne out by observations from South Africa – that the decline during the second wave was in part due to less conducive weather conditions during summer and that infections could resurge (which is indeed occurring) during winter. For India, the model estimates two seasons (i.e., the monsoon season during June – September and winter during December – January) would experience higher virus transmission; this seasonality in combination with the implemented NPIs explain much of the COVID-19 pandemic dynamics observed thus far in India.…”

The Effects of Climate and Bioclimate on COVID-19 Cases in Poland

“…Many of these studies were limited by short observation periods, either taking into account varying reporting biases, or failure related to the time lag between observed weather conditions and the acquired data reports concerning cases of infections and death. The reported observations were confirmed by laboratory evidence on the stability of SARS-CoV-2 as a function of temperature and humidity, proving that the virus's half-life in human nasal mucus and sputum is shorter under higher temperature conditions and relative humidity than under conditions of lower temperature and relative humidity [9]. Moreover, during winter people spend more time indoors, which may make the virus act Remote Sens.…”

“…Nevertheless, numerous other studies have found either positive or negative associations of air temperature, humidity, and UV radiation with reported COVID-19 case numbers [9][10][11][12][13][14][15]. Many of these studies were limited by short observation periods, either taking into account varying reporting biases, or failure related to the time lag between observed weather conditions and the acquired data reports concerning cases of infections and death.…”

Pathogenesis of Respiratory Viral and Fungal Coinfections

“…This variation in incidence might be explained by the interplay of a number of factors with the copathogenesis of respiratory viral and fungal coinfections, including differences in environmental and/or genetic factors, type of circulating viral strain, treatment modalities for the critical illness, and the use of and access to fungal diagnostic tools. Environmental conditions can modulate host immune responses, including mucociliary clearance, tissue repair functions, and innate immune defenses ( 498 ), as well as outbreaks of viral respiratory diseases by influencing virus stability and transmission rates ( 499 – 501 ). Seasonal fluctuations in airborne fungal spore levels have also been determined for different genera, with the dominant genera varying depending on geographical location ( 502 – 510 ).…”