Impact of climate change on SARS-CoV-2 epidemic in China

whereas the western side comprised only approximately 6% of the population, which is consis- tent with the spatial distribution of epidemic severity. The Hu Line segregates the level of population density from the social and economic pat- terns in China. Furthermore, it segregates the urbanization levels (as shown in S7 Fig). After more than half a century of development, the population in west China increased by only 2%, and the economic disparity widened. Most provinces and cities in the southeast indicated urbanization levels above the national average, whereas those of most regions in the northwest were below the national average. This is attributable to differences in the population density. However, it revealed the integrated pattern of natural, human, economic, and social factors in China, particularly the weather and landscape, which are important factors, thus resulting in a significant difference in the natural ecology. The spatial distribution of the GR in the south- eastern region of China shows a more intense pattern compared with that in the northwestern region, which is consistent with the area delineated by the Hu Line. This indicates the effect of the urbanization level on SARS-CoV-2. Owing to accelerated urbanization, rapid population and economic development, as well as the uncontrolled exploitation of the natural environment, humans are constantly considering the ecological resources of other organisms. Intense human activities have disrupted the bal- ance of ecosystems, increased environmental risks and the migration of virus–host habitats, as

well as increased the probability of viral mutations and the risk of infectious disease outbreaks. Simultaneously, the cluster of different viruses hosted after habitat migration significantly increases the probability of virus mutations and the risk of new infectious disease outbreaks. Studies have suggested that low precipitation and food shortages may cause animals to congre- gate around scarce resources, which increases host-to-host contact for viral transmission [42]. Effect proportion of weather factors on SARS-CoV-2 Environmental and climate changes can significantly affect ecosystems. Their effects on the occurrence, transmission, and changes in infectious diseases are among of the most detrimen- tal to health [43]. Infectious diseases comprise three main elements: pathogens, hosts, and transmission routes. Therefore, changes in climate or weather conditions may affect infectious diseases depending on the environment in which they exist [44]. Climatic conditions limit the geographic and seasonal distribution of infectious diseases, whereas environmental and mete- orological factors may affect the timing and intensity of disease outbreaks [45]. According to the principles of epidemiological transmission, physical isolation is the most direct and effective method for disease control. The implementation of the home exclusion policy in China resulted in an effective control of person-to-person transmission of SARS-- CoV-2. Policy regulations imposes a direct but short-term effect in preventing and managing

the SARS-CoV-2 epidemic, whereas climatic factors imposes a long-term indirect effect. Path- ologically, UV-C exerts an inhibitory effect on SARS-CoV-2 and has been used in disinfection procedures in hospitals and laboratories [16]. UV radiation is solar radiation in the wavelength band between 100 and 400 nm and is typically classified into three categories: UV-A (320–400 nm), UV-B (280–320 nm), and UV-C (100–280 nm). UV-C is mainly completely absorbed. A considerable amount of UV-A directly reaches the ground and can tan the skin, produce vita- min D, and affect photosynthesis. UV-B is mainly absorbed; however, even if this radiation reaches the ground in small amounts, it can cause significant environmental and ecological effects, as well as affect human health [46]. Carleton et al. [25] showed that for every one unit increase in UV radiation worldwide, the GR decreased by 13.2% over 17 days (0.78% per day). However, the UV impact in China was higher than the worldwide level, with a decrease of 18.65% over 11 days (1.70% per day), i.e., 0.92% higher than the world average per day. PLOS ONE Impact of climate change on SARS-CoV-2 epidemic in China PLOS ONE | https://doi.org/10.1371/journal.pone.0285179 July 27, 2023 16 / 21