COVID-19 and its association with meteorological, climate, and environmental factors: A systematic review

COVID-19 transmission can be influenced by various factors, including weather and climate conditions, population density, and the availability of medical facilities. To gain a deeper understanding of this topic, an in-depth analysis of recent studies is needed. Our objective was to investigate previous systematic reviews that have examined the seasonal variation of COVID-19 and the impact of climate on its transmission and mortality. Online databases that included PubMed, Scopus, Web of Science, and Cochrane were searched using relevant keywords up to November 2021. Negative associations were found between temperature and COVID-19 spread and mortality (6/9 studies, 66.6%). These negative correlations imply a decrease in the spread and mortality of COVID-19 with an increase in temperature. Similarly, seven systematic reviews reported a negative correlation between humidity and transmission or mortality of COVID-19 (7/9 studies, 77.7%). COVID-19 spread was not associated with precipitation (three studies) but was negatively correlated with sunlight or UV radiation (two studies), COVID-19 incidence and mortality were positively associated with wind speed (one study). One study reported that the effect of air pressure and UV radiation on COVID-19 activity was unknown. The effects of air pollution, seasonal changes, wind speed, precipitation, and UV radiation on COVID-19 incidence or mortality remain unclear. However, factors proposed as having the greatest influence on COVID-19 incidence or mortality include air pollution, wind speed, and wastewater. Sunlight exposure and warm climates likely assist with reducing COVID-19 incidence or mortality, with the infection having a winter seasonality.