How Temperature Affects the Spread of COVID-19
Intro
SARS-CoV-2 is a branch of the SARS-Cov family. It is spherical and enveloped with club-shaped spikes on the surface. Thus, it has the shape of a solar corona. Inside the nucleoplasm, the virus has single-strand RNA, which stores the genetic information of this virus. Due to the property of protein and RNA, the SARS-CoV-2 should have been sensitive to temperature. According to the data of thirteen countries, there’s some relationship between temperature and the spread of COVID-19 (Kassem, Aly Zein Elabdeen, 2020).
However, is this conclusion convincible and conclusive? Let’s have dive into it and have a look.
How temperature may affect the SARS-CoV-2
As the data of thirteen countries demonstrated, there’s an inverse (negative) with temperature and the spread of COVID-19 (Kassem, Aly Zein Elabdeen, 2020). The researchers collected the hospitalization data of COVID-19 in different countries from January 2020 to March 2020. With the obtained data, they performed the Nonlinear-Least-Squares regression to explore the relationship between temperature and the spread of COVID-19. As the results demonstrated, there is an inverse relationship between the independent variable(temperature) and the dependent variable (case per million). However, the result won’t be significant until 164.8 days after the beginning of the pandemic.
Now that we’ve found a negative relationship between temperature and the spread of COVID-19, is it safe to conclude that high temperature will prevent the transmission of COVID-19? Maybe not. According to another research performed in Oslo, Norway, the scientists got the opposite result. In this research, the scientists collected data from the Norwegian public health institute database and weather data from the Norwegian Meteorological Institute for February 27–May 2, 2020. Then, the researchers performed a Pearson correlation for the data. As the research shows, average temperature, minimum temperature, lowest wind speed，, and highest wind speed is not significantly correlated with the spread of COVID-19.
Nevertheless, low precipitation and maximum temperature are statistically associated with the number of infectious cases (Menebo, 2020). This contradicts the intuition of researchers, so they come up with an alternative explanation: high temperature and low precipitation would encourage people to come out and break the “stay-at-home” rule. Thus, precipitation is negatively correlated with the spread of COVID-19, and temperature is positively associated with it.
However, even if both of them make sense, we should still consider other variables. Imagine we are investigating two specific objects. In our intuition or subconsciousness, we assume there’s some specific relationship between them. Yet, it is possible that there’s no correlation at all. In another research, Mecenas et al. Collected data and articles from different journals and websites since the outbreak of COVID, including PubMed, Scopus, Web of Science, Cochrane Library, LILACS, OpenGrey, and Google Scholar. These scientists performed a Risk Bias Assessment and found few (2) studies have a high risk of bias, some (11) studies have a moderate risk of bias, and four studies were classified as low-risk bias. Even if they found that not all researches are completely convincible, they acknowledge that weather and humidity should have great value in the research of COVID-19.
To some extent, warm weather and higher humidity may restrict the treamission of COVID-19 (Mecenas et al., 2020). In comparison, the researchers came up with some more questions worth thinking about. First, these data are collected after the outbreak in China. At that time, the Chinese government implemented strict lock-down. Thus the data may not be used for reference. Also, they’re much fewer cases reported in the tropical area. But that’s not because there are truly fewer cases. Instead, maybe those underdeveloped countries in the tropical area don’t have enough methods to diagnose and report it. All these variables may affect those existing models untenable (Mecenas et al., 2020).
Why Temperature Can Influence the Spread of COVID-19
Up to now, scientists are not confident enough to draw a conclusion about how temperature affects the spread of COVID-19. However, the temperature can truly affect our immune system, and this may play an important role in the transmission of COVID-19.
First, cold weather might be more suitable for coronavirus to survive (Araújo, Naimi, 2020). Second, cold weather may force vasoconstriction of the respiratory tract and weaken the immune system at the same time. Plus, cold air may cause small ruptures on mucosa and foster the proliferation of the virus (Bu et al., 2020). What’s more, cold weather is always accompanied by other diseases, like flu. And these diseases may trigger the development of SARS-CoV-2. So, cold weather should play a role in the transmission of COVID-19.
Nonetheless, reflecting on what we said in the beginning, is it possible to “kill” coronavirus at a high temperature? The answer is partial “Yes.” As we know, the major component of SARS-CoV-2 is protein, and protein may denature in high temperatures. Yet, what is “high temperature”? It may have a wide range. Sometimes, the interaction of the peptide bond may be affected at 41 Celcius. However, they will not denature completely until 101 Celcius (Chemistry Explained, 2020) for some proteins. And according to the research of NIH, if we want to kill coronavirus with high temperature, we need to expose it at least 3 minutes when the surrounding temperature is 75 Celcius or 5 minutes when the temperature is 65 Celcius, and 20 minutes when the temperature is 60 Celcius and above (Abraham et al., 2020). It is rare (even impossible) to reach 60 Celcius degrees in our daily life. So, warm weather is not the direct factor that eliminates coronavirus.
The possible treatments we can take
According to Mecena et al., although current studies found a correlation between temperature and humidity, the result is not conclusive enough. First, the data generated are biased because the researchers focused on only two variables: temperature and humidity. There are so many variables in the transmission process of the epidemic, such as population density, topology, and even local governments’ policies. Second, the criteria of temperature are uncertain in this research. The scientists did found a negative relationship between temperature and the spread of COVID-19, yet they don’t have a specific definition of “high” and “low” temperature, especially when they don’t know the average temperature of one area.
Considering what we’ve discussed above, even if some scientists are not optimistic about the effect of high temperature, and there’s truly no evidence that we can kill coronavirus with high temperature, scientists still think there should be a relationship between weather and the spread of COVID-19.
As for us, we can avoid being exposed to cold weather to prevent respiratory diseases, keep working out to improve our immune system, and stay social-distancing in such a “viral era”.
References:
Kassem, Aly Zein Elabdeen. “Does Temperature Affect COVID-19 Transmission?.” Frontiers in public health vol. 8 554964. 22 Dec. 2020, doi:10.3389/fpubh.2020.554964
Menebo, Mesay Moges. “Temperature and Precipitation Associate with Covid-19 New Daily Cases: A Correlation Study between Weather and Covid-19 Pandemic in Oslo, Norway.” Science of the Total Environment, vol. 737, 2020, doi:10.1016/j.scitotenv.2020.139659.
Paulo Mecenas, et al. “Effects of Temperature and Humidity on the Spread of Covid-19: A Systematic Review.” Plos One, vol. 15, no. 9, 2020. INSERT-MISSING-DATABASE-NAME, INSERT-MISSING-SERVICE-NAME, doi:10.1371/journal.pone.0238339. Accessed 14 June 2021.
Araújo MB, Naimi B, “Spread of Sars-Cov-2 Coronavirus Likely to Be Constrained by Climate.” Medical Letter on the Cdc & Fda, vol. 615, 2020, pp. 615–615.
Bu J, Peng D, Xiao H, et al. Analysis of meteorological conditions and prediction of epidemic trend of 2019-nCoV infection in 2020. medRxiv: 20022715v1 [Preprint]. 2020. Available from: https://www.medrxiv.org/content/10.1101/2020.02.13.20022715v1.
Denaturation. Chemistry Explained. (n.d.). http://www.chemistryexplained.com/Co-Di/Denaturation.html.
Abraham, John P et al. “Using heat to kill SARS-CoV-2.” Reviews in medical virology vol. 30,5 (2020): e2115. doi:10.1002/rmv.2115
