The Relationship between Ambient Temperature and Positive Cases of COVID-19; A Case Study in Abarkouh and Qeshm Cities of Iran

1 Environmental Science and Technology Research Center, Department of Environmental Health Engineering, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. 2 Genetic and Environmental Adventures Research Center, School of Abarkouh Paramedicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. 3 Department of Environmental Health, Payambar Azam Qeshm Hospital, Hormozgan University of Medical Sciences, Bandar Abbas, Iran. 4 Health Office of Qeshm, Hormozgan University of Medical Sciences, Bandar Abbas, Iran. 5 Research Center for Environmental Determinants of Health (RCEDH), Health Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran.


Introduction
Viruses are a major cause of acute and chronic illnesses in human beings. They are common pathogens in hospital environments, health care services, and in crowded places with poor hygiene such as schools and kindergartens [1][2][3] . Most viral infections are subclinical and asymptomatic; however, mild viral illnesses can put a heavy burden on the economy and health care systems 4 . The mild viral illnesses are an important predisposing factor for more serious and perhaps secondary fatal bacterial infections 5 .Viral infections cause 60% of the human infections, most of which are caused by respiratory and intestinal viruses 6,7 . Annually, 1.7 million deaths are reported from diarrhea diseases and 1.5 million deaths are caused by respiratory infections worldwide 8 . Several factors can affect environmental pollutants 9 and spread of viral infections that include unsanitary conditions, susceptible host, population congestion, high infectivity of viruses even at low doses, as well as excretion of viruses from the infected person before the onset of symptoms until several days after recovery 10 . In December 2019, the main outbreak center of Coronavirus disease 2019 (COVID 19) (SARS CoV-2) was Wuhan, Hubei province 11 . The virus began to spread rapidly among countries, with a much higher prevalence than severe acute respiratory syndrome (SARS) 11 . The global prevalence of COVID 19 has created many barriers to public health and the global economy 12 . To control the prevalence of COVID 19, biological characteristics of the virus should be investigated in the natural environment, especially in the outbreak time. Temperature is an important factor influencing the survival of micro-and macro-organisms that can play an important role in the spread and control of epidemics 13 . The viability of micro-organisms varies in different environments and temperatures 10 . Temperature and humidity of the environment are effective factors on the outbreak of COVID19. At the beginning of the outbreak, countries with lower temperatures and humidity (such as Korea, Japan, and Iran) had a higher prevalence rate than warmer countries with high humidity (such as Singapore, Malaysia, and Thailand) 14 . Based on previous studies, at the time of SARS outbreak in 2003, the number of infected people in areas with low temperatures was 18.18 times higher than those who lived in areas with higher temperatures 15 .
The aim of this study was to investigate the positive cases of COVID19 and its correlation with the ambient temperature in two cities of Abarkuh and Qeshm with different average temperatures in a 49-day period.

Materials and Methods
This descriptive-analytical study was carried out in two cities of Abarkouh and Qeshm with a population of 51199 and 45178, respectively. To conduct the study, the number of positive cases (confirmed by a testing kit and CT scan) and the air temperature were examined from February 20 th to April 8 th . The relationship between the number of positive cases and the ambient temperature was analyzed using descriptive statistics and correlation coefficient tests by SPSS (version16.0.).

Results
During the studied period, the average ambient temperature for Abarkouh and Qeshm cities were 19.16 ± 3.45℃ and 25.79 ± 1.83 ℃, respectively. Moreover, the number of positive cases were 38 and 28 in Abarkouh and Qeshm, respectively (Table 1). With regard to Abarkouh City, statistical analysis showed that the correlation between ambient temperature and number of positive cases was determined as -0.107. Furthermore, the rate of determination was 0.011, which indicates that 1.1% of the changes in the dependent variable (the numbers of positive cases) can be expressed by the ambient temperature. Figure 1a illustrates the correlation between temperature and the number of positive cases. The correlation between the number of positive cases and the daily temperature is represented in Figure 1b.

Considering
Qeshm, statistical analysis revealed that the correlation between the ambient temperature and the positive cases was -0.083 and the rate of determination was 0.007. In other words, 0.07 percent of the dependent variable (the number of positive cases) is expressed by the ambient temperature. Figure 2a illustrates the correlation between temperature and the number of positive cases. Figure 2b shows the correlation between the number of positive cases and the daily temperature during the study period. Correlation between the number of positive cases and daily temperature during the study period in Qeshm City

Discussion
According to the findings, the ambient temperature of Abarkouh City had higher thermal turbulence compared to Qeshm City in the study period; the ambient temperature varied from 9 to 25 ºC with an average of 19.16 ± 3.45 ºC in Abarkouh City. The city of Qeshm had lower thermal turbulence with a high average temperature of 25.79 ± 1.83. The comparison of the number of positive cases between these two cities revealed that the percentage of positive cases in Qeshm was 15% lower than that of Abarkouh. Results of the correlation test between temperature and the number of positive cases in the studied cities showed that the number of positive cases decreased by increase of temperature (Figures 1a and 2a). The correlation between temperature and the number of positive cases was more obvious in Abarkouh due to higher thermal turbulence. The daily temperature comparison chart and the number of positive cases (Figures 1b and 2b) also indicate an increase in the definite number of COVID 19 cases when the average temperature decreases. According to previous studies, high temperature and humidity reduce the rate of transmission and spread of influenza [16][17][18] , which can be justified by the following justifications. First, influenza is more stable at low temperatures and humidity 19,20 and second, wet and cold weather can weaken the host's immune system and make the person more vulnerable to the virus 21,22 . Moreover, the literature indicated that increase of the ambient temperature and humidity reduced the viability of SARS coronavirus 23,24 . In addition to the epidemiological studies, laboratory studies have also confirmed this finding 18,[25][26][27] . Moreover, infectivity of the virus increases under low temperature and humidity conditions. The results of a study on swine flu revealed that the infection rate at a temperature of 5 ºC and humidity of 35-50 % was in the range of 75 to 100%. However, with an increase of temperature to 30 ºC and humidity to 35%, the infectious rate was zero 28 . Another study found that three key factors of temperature, humidity, and wind speed were effective in the spread of SARS virus 24 . A laboratory study of the SARS virus reported that the virus could remain active on smooth surfaces for at least 5 days at the temperature of 22 to 25 ºC with the humidity of 40 to 50%. In the case that the temperature elevated to 38 ºC and the relative humidity increased to 95%, the virus lost its activity quickly 23 . Another study published in 2013 found that Middle East Respiratory Syndrome virus remained active for a long time under low temperature and humidity conditions 29 . Wang et al. also investigated the effect of high temperature and humidity. Based on their results, high temperature and humidity reduced the transmission of COVID-19 14 .

Conclusion
The correlation between the number of positive cases of COVID 19 and temperature was investigated in Abarkouh and Qeshm cities during a 49-day period. Based on the findings, the number of positive cases were decreased by increase of the ambient temperature in both cities. In Abarkouh, the relationship between the number of positive cases and the air temperature was more obvious due to the higher thermal turbulence. A significant decrease is expected in the number of positive cases in the coming days and months due to the increase of ambient air temperature, which is unfavorable for the virus survival.