Effects of temperature variation and humidity on the mortality of COVID-19 in Wuhan

Yueling Ma; Yadong Zhao; Jiangtao Liu; Xiaotao He; Bo Wang; Shihua Fu; Jun Yan; Jingping Niu; Bin Luo

Respiratory diseases mortality increased with decreasing temperature [24], and was strongly associated with low temperature [25-27]. While another study found that both cold and heat effects may have adverse impact on respiratory mortality [28] . Otherwise, the study conducted in 30 East Asian cities showed that increased DTR was associated with increased risk of mortality for respiratory and cardiovascular diseases [29] . In the cold season, the cumulative relative risk of non-accidental, respiratory and cardiovascular death increased at high DTR values in Tabriz [30] . A time-series study done in Shanghai on the effect of DTR and daily chronic obstructive pulmonary disease (COPD) mortality showing that each 1°C elevation in the 4-day moving average for DTR accounted for 1.25% of increased risk of COPD mortality [31] . A review for cold exposure and immune function reported that lower temperature may repress the immune function [32] , particularly, our previous finding suggested that the phagocytic function of pulmonary alveolar macrophages declined under cold stress in vitro experiment [33] . Breathing cold air can lead to bronchial constriction, which may promote susceptibility to pulmonary infection [34] . Additionally, since SARS-CoV-2 is sensitive to heat, and high temperature makes it difficult to survive, not to mention the beneficial factors for virus transmission like indoor crowding and poor ventilation in cold days [35] . Also, cold temperature has been discovered to be associated with the reduction of lung function and increases in exacerbations for people with COPD [36] . In addition, DTR represents a stable measure of temperature, which is an indicator of temperature variability to evaluate effects on human health, including mortality and . CC-BY-NC-ND 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity.