Several previous studies indicated that there is a relationship between climate and the spread of certain types of germs, and viruses that cause diseases, and this is especially true for malaria, which only spreads under certain weather conditions in terms of temperature and humidity. There is no doubt that there are a large number of diseases, the spread of which is associated with certain seasons. It was also noticed that the common flu increases in cold shows than in hot tropical shows(). Also, Oliver notes that most of the deaths that occurred in England and Wales due to heart disease and respiratory disease occurred in the winter months between November and March.()
A severe respiratory disease was recently reported in Wuhan, Hubei province, China. As of 25 January 2020, at least 1,975 cases had been reported since the first patient was hospitalized on 12 December 2019, Epidemiological investigations have suggested that th e outbreak was associated with a seafood market in Wuhan. Phylogenetic analysis of the complete viral genome revealed that the virus was most closely related (89.1% nucleotide similarity) to a group of SARS-like coronaviruses (genus Beta coronavirus, subgenus Sarbecovirus) that had previously been found in bats in China. The sequences are almost identical and share 79.6% sequence identity to SARS-CoV. Furthermore, Researchers show that 2019-nCoV is 96% identical at the whole-genome level to a bat coronavirus. This outbreak highlights the ongoing ability of viral spill-over from animals to cause severe disease in humans.().It appears that most of the early cases had contact history with the original seafood market.()
There is a relationship between air humidity and the life of bacteria and viruses. The influenza virus dies more quickly in conditions of high humidity accompanied by fast moving air, so the winter months in which humidity decreases and the speed of air movement decreases are more appropriate for the spread of respiratory infections(). It was also found that the TB germ, if exposed to sunlight, stops its activity within one hour. Whereas in the normal light, it remains active between 6–24 hours, and in the dark, it lives in a state of activity between two and eighteen months, so chest diseases hospitals must be established in sunny areas. (1)
Compared to the 2002/2003 SARS-CoV and the 2012–2014 MERS-CoV (Middle East Respiratory Syndrome-related coronavirus), the COVID-19 coronavirus spread strikingly fast. While MERS took about two and a half years to infect 1000 people, and SARS took roughly 4 months, the novel SARS-CoV-2 reached that figure in just 48 days. On 30 January 2020, the World Health Organization (WHO) declared that the new SARS-CoV-2 coronavirus outbreak constitutes a Public Health Emergency of International Concern (PHEIC) (). As of 2 March 2020, more than 89,000 COVID-19 cases have been reported globally, from all provinces of China and 66 countries globally. Global outbreaks of COVID-19 have posed major obstacles to public health and the world economy(). As of 30 Mars 2020 720,000 cases had been reported globally including 177 countries about 34,000 of them died ().An increase of 631,000 cases over 28 days, with an average of about 22550 cases per day.
Multiple countries have confirmed travel-associated cases, including Australia, Cambodia, Canada, France, Germany, Japan, Nepal, Singapore, South Korea, Taiwan, Thailand, United Arab Emirates, United States, and Vietnam. Vietnam identified the first human-to-human transmission outside China()..As of 30 Mars 2020 The highest cases were recorded in United States of America, Italy, and china.
(Jin Bu et al) find that the suitable temperature range for 2019-nCoV survival is (13–24 °C), among which 19 °C lasting about 60 days is conducive to the spread between the vector and humans; the humidity range is 50%-80%, of which about 75% humidity is conducive to the survival of the coronavirus; the suitable precipitation range is below 30 mm/ month. The prediction results show that with the approach of spring, the temperature in north China gradually rises, and the coronavirus spreads to middle and high latitudes along the temperature line of 13–19 °C ().
"Jingyuan Wang et al" find that after estimating the serial interval of COVID-19 from 105 pairs of the virus carrier and the infected, they calculate the daily effective reproductive number, R, for each of all 100 Chinese cities with more than 40 cases. Using the daily R values from January 21 to 23, 2020 as proxies of non-intervened transmission intensity, they find, under a linear regression framework for 100 Chinese cities, high temperature and high relative humidity significantly reduce the transmission of COVID-19, respectively, even after controlling for population density and GDP per capita of cities. One degree Celsius increase in temperature and one percent increase in relative humidity lower R by 0.0383 and 0.0224, respectively(7).
Comparison of meteorological conditions of the onset of 2019-nCoV pneumonia in 2019 and SARS pneumonia in 2003, from October to November 2019 in Wuhan, the mean temperature in Wuhan dropped from 18.28 °C to 13.43 °C. Humidity remained between 73.12% and 77.58%, and the first few cases of the 2019-nCoV pneumonia occurred in early December. The meteorological conditions significantly overlapped with those of SARS onset in Guangzhou. In the winter of 2002, the temperature was between 13.85 °C to 15.85 °C, and humidity kept between 69.05% and 78.91% in Guangzhou. Considering the data above including 2019-nCoV in Wuhan, SARS coronavirus in Guangzhou and Beijing, we speculate that a meteorological condition with temperature between 13–19 °C and humidity between 50% and 80% is suitable for the survival and transmission of the coronavirus. (Jin Bu, et al, 2020) Lower rainfall and therefore reduced relative humidity provide a good opportunity for the transmission of respiratory pathogen infections, including coronavirus. ()