There are three possible answers to this question: 
1. Yes, temperature does affect the spread of SARS-CoV-2. There is a positive/negative relationship 
2. No. There is no clue/ there is no significant statistical relationship between temperature and the spread of SARS-CoV-2.
3. We don't know

Did temperature affect the spread of  SARS-CoV-2 VIrus?

Frontiers in public health vol. 8 554964. 22 Dec. 2020, doi:10.3389/fpubh.2020.554964

Does Temperature Affect COVID-19 Transmission?

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.

Temperature and Precipitation Associate with Covid-19 New Daily Cases: A Correlation Study between Weather and Covid-19 Pandemic in Oslo, Norway.

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. 

Analysis of Bias

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.

Effects of Temperature and Humidity on the Spread of Covid-19: A Systematic Review.

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.

How Does Temperature Affect SARS-Cov-2 VIrus Itself?

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.

Analysis of meteorological conditions and prediction of epidemic trend of 2019-nCoV infection in 2020

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.

Other Factors Accompanied with Cold Weather that Might Affect the Spread of SARS-CoV-2

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 be sensitive to temperature.

Ohio State University, Columbus

COVID-19 is spread through person-to-person transmission. The virus spreads mainly through close personal contact (such as when people are within 6 feet of one another) and through the respiratory droplets of someone infected with COVID-19.  Aerosol transmission is also likely, but the relative contribution of these smaller respiratory particles is not completely understood. While less common, spreading can also occur when people touch contaminated objects or surfaces and then their faces, eyes, or mouth. 

Transmission of COVID-19

1. [MODULE 1: From Bench to Bedside, Section: 'GRAPHIC SUMMARY' (as of March 19, 2020)](https://docs.google.com/document/d/1gjUuqTLi7xqMVzgWeYAFulmaIiKzhYY89PVOJJVvlNo/edit#heading=h.gtn0tdsnrc43)
2. [MEDICAL STUDENT COVID-19 CURRICULUM](https://docs.google.com/document/d/13JfRRw1GEIKz4JCde8WcQBCHnu-7nn11P_z0dHov1eA/preview)


COVID-19 Graphical Summary

The reproductive/reproduction number of COVID-19 is estimated to be between 2 and 2.5 as of March 6, 2020. 

Reproductive Number of COVID-19

- American Association for the Advancement of Science

- American Veterinary Medical Association (AVMA)

- Asian Pacific Journal of Tropical Medicine (APJTM)

- BioMed Research International

- BioRxiv (Preprint)

- Emerging Infectious Diseases

- Environmental Research 

- Forensic Science International: Reports

- Infectious Disease Modeling 

- Infectious Diseases Society of America (Clinical Infectious Disease)

- Jama Network Open

- Journal of Travel Medicine

- Nature Communications

- Risk Analysis

- Science of the Total Environment

- Social Science Research Network (SSRN)

- The International Journal of Infectious Diseases  

- The Journal of the American Medical Association (JAMA)

- The Lancet

- The Lancet Infectious Diseases 

- The New England Journal of Medicine

- Travel Medicine and Infectious Diseases

- Veterinary Quarterly

- Virology Journal 

- World Journal of Clinical Cases




Transmission of COVID-19 References by journal

Cluster transmission has been noted in many COVID-19 studies
It is characterized by infections that are concentrated within a given area, often within families or social circles 

Cluster Transmission of COVID-19

- Asia
- Africa 
- North America
- South America
- Antarctica
- Europe
- Australia

Classification of studies on COVID-19 Transmission by Continents

Indirect Transmission of COVID-19

Previous reports indicate that asymptomatic transmission is possible, but since they’re hard to track, this poses a significant challenge to infection control practices.

Implications of Asymptomatic COVID-19 Transmission

- Super spreading events

- Climate

- Season

- Location

- UV & sunlight on the virus

- Virus concentrations in wastewater 

Factors that affect the transmission of COVID-19

Live animal food markets carry a great risk of transmitting zoonotic diseases compounded by the lack of safe and regulated hygienic practices. The Huanan South Seafood Market in Wuhan, China which sells wild exotic and domesticated live animals for consumption, was identified to be the epicenter of the COVID-19 pandemic. Bats are implicated to be the reservoir hosts of the virus, as SARS-CoV-2 is 96% genetically identical to bat coronavirus. Pangolins are also a possible host, as the RBD in the S protein show similarity to Pangolin-CoV. 

Any infections in animals with COVID-19 should be reported to the World Organization for Animal Health (OIE). The CDC reports that a number of pets worldwide are confirmed positive for COVID-19, though the risk of animal-human transmission in these cases are yet unclear.

Zoonotic Transmission of COVID-19

In a comprehensive case study, Vivanti et al. report the first transplacental transmission of SARS-CoV-2 with clinical manifestation in the newborn, consistent with neurological signs and symptoms of the virus. 

Transplacental Transmission of COVID-19

Determining this has critical implications: 

If primarily spread via droplets, then masks, distancing rule (6ft), etc. are effective in preventing transmission. Conversely, if primarily spread via aerosols, then preventative measures become less effective and thus need to be modified. 

Examining the source of transmission for both types of respiratory particles are crucial.



Aerosol versus Droplet Debate

Transmission of COVID-19 references by organization

Current data shows that infection rates of SARS-CoV-2 are low among children. It then can be said that they do not play a prominent role in the disease transmission of COVID-19 during the pandemic. Although the actual infection rate cannot be known due to under-reporting and a lack of available results from seroepidemiological studies, there are numerous findings against an increased risk of infection from children and findings that show a lower rate of infection and of contagion especially in children under the age of 10. It was also found that the transmission of SARS-CoV-2 is typically from an infected adult to a child and that a lack of evidence remains for the transmission of infection from an infected child to an adult. The cause of this lower virus transmission rate is still unknown, which calls for further investigations. 

Role of Children In Transmission

- Genomic Evidence of In-Flight Transmission of SARS-CoV-2 Despite Predeparture Testing
-  In-flight transmission of SARS-CoV-2: a review of the attack rates and available data on the efficacy of face masks

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