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The question of how the coronavirus is affected by the temperature of the environment, as well as the blood inside the host’s body, is still being discussed. This is important in order to develop ways to neutralize the virus in the external environment and effectively select treatment methods, given that for many people with COVID-19, a temperature rise to high numbers is typical.
Many hoped that the new coronavirus would disappear in the summer as summer weather became warmer and wetter. Despite the fact that the virus does not tolerate heat well, summer temperatures have not stopped the pandemic1.
Some strains of the virus (British, Brazilian, Indian) may change depending on the environment. They can survive and thrive in different geographic regions or climates. It’s impossible to accurately predict how a virus reacts to heat and humidity, or, for that matter, cool and dry temperatures outside of laboratory experiments.
In countries such as Australia and Iran, COVID-19 spread very quickly at the beginning of the pandemic despite warm and humid weather. Every virus and pandemic is unique, and there are a number of factors that affect them, regardless of the time of year. That’s why experts recommend continuing to take appropriate steps to protect yourself and those around you throughout the year.
US researchers have shown that the SARS-CoV-2 coronavirus — the agent that causes coronavirus disease 2019 (COVID-19) — can be rendered unable to infect a host if exposed to very high temperatures for less than a second. As reported in the journal Biotechnology and Bioengineering, a Texas A&M University team has developed a simple fluid system that heat-inactivates coronaviruses in less than a second.2.
If a solution containing the coronavirus is heated to about 72 degrees Celsius for about half a second, it can reduce the titer or amount of virus in the solution by a factor of 100000. Applying a temperature just above 83 °C for one second reduced the virus titer by more than a million times and completely inactivated the virus.
This study provides important data for the development of approaches to thermal inactivation of CoV, including the development of methods for the effective inactivation of indoor airborne viruses.3.
Sterilization methods currently in use
The main routes of SARS-CoV-2 transmission include contact with contaminated surfaces, person-to-person transmission by coughing or sneezing, and airborne transmission via aerosol particles. Environmental sterilization and virus inactivation are critical to preventing and controlling the spread of the virus. Methods currently used include the use of chemical treatment, exposure to UV radiation and heat treatment.
Heat treatment denatures the viral proteins that make up the virion, making the virus unable to infect the host. Compared to other methods, significant advantages of heat treatment include the relatively shorter time, simplicity and safety of the method, and the ability to integrate into existing systems such as heating, ventilation and air conditioning systems.4.
Fever is one of the most effective responses to infections in humans and has evolved over 600 million years. This is a complex physiological response triggered by the body to increase metabolism and increase core body temperature. Physicians describe fever in 42,8% of patients on presentation and in 88,7% of patients with COVID-19 at the time of admission. This suggests that while fever is the most common symptom in patients with COVID-19, its absence during initial screening does not rule out COVID-19.
It is known that viruses multiply most actively at a body temperature of 37 degrees (remember that the temperature of the skin and the internal environment of the body differ by about 0,5-1 degrees). Accordingly, the virus is most comfortable at normal body temperature. Therefore, the body includes protective mechanisms – febrile reactions. It is known that an increase in temperature by 1 degree slows down the reproduction of viruses several times, and a temperature of 39 degrees and above completely suppresses the activity of viruses. But, of course, such a fever is dangerous for the person himself.
With satisfactory health, it is not recommended to bring down the temperature for adults to a limit of 38,5 degrees so that the body can suppress the activity of the virus. As the body clears the virus, so does the temperature.
Doctors have reported an average duration of fever in COVID-19 patients of 8 to 11 days. Temperature drop coincided with PCR-negative upper respiratory specimens5.
The effect of fever or ambient temperature on other viruses has been previously studied. Coronaviruses will behave similarly. In experimental models in mammals, it has been shown that a higher ambient temperature increases resistance to herpes simplex virus, poliovirus, Coxsackie B virus, rabies, influenza.
Based on a human study, it was found that the use of antipyretic drugs to suppress fever would increase influenza morbidity and mortality, the use of aspirin and paracetamol was associated with increased nasal symptoms and decreased neutralizing antibody response. In another randomized clinical trial involving 72 children, the use of paracetamol was associated with an increase in the duration of rashes in childhood varicella infection.
The role of fever in COVID-19 has not been studied in large studies. Only two studies have linked ambient temperature or fever to treatment outcomes in patients with COVID-19. In an observational study, high ambient temperature correlated with a decrease in mortality in COVID-19 patients in Wuhan and Hubei provinces. However, the study did not have data on the patient’s temperature, which limits any conclusions.
Persistent high fever with COVID-19 is considered an indicator of severe infection. In a study of 201 patients in Wuhan, high fever (>39°C) was associated with a higher likelihood of developing acute respiratory distress syndrome and a lower risk of death. Preliminary results may indicate improved prognosis in terms of mortality in patients with severe febrile COVID-19.
The initial manifestation of fever in COVID-19 in the first week, during the viral phase of the disease, is likely due to the manifestation of the body’s immune response to viral replication to increase resistance. However, if the viral infection persists, the course of the disease is complicated by a state of unregulated inflammation, described as a cytokine storm.
In such cases, when severe inflammation sets in, fever can be counterproductive. Fever can promote further inflammation and further activation of the immune system at this stage can be turned against the patient.5.
Expert Commentary
“According to the latest data, the coronavirus dies at a temperature of 60 ° C and above, for example, when washing clothes,” says allergist-immunologist Ksenia Bocharova. – When dried, when exposed to UV radiation, it dies within 24 hours.
In general, the best defense against coronavirus infection is still keeping a distance.
“The virus itself is a large particle,” explains Ksenia Bocharova. – When talking, coughing, sneezing, viruses scatter not far from a sick person, and they fall mainly on the floor within about a meter.
Sources:
- National Academies of Science, Engineering, and Medicine: «Rapid Expert Consultation on SARS-CoV-2 Survival in Relation to Temperature and Humidity and Potential for Seasonality for the COVID-19 Pandemic (April 7, 2020) (2020).
- Jiang Y, et al. Sub‐second heat inactivation of coronavirus using a betacoronavirus model. Biotechnology and Bioengineering, 2021. Doi: https://doi.org/10.1002/bit.27720
- Bogdan C. Pană, Henrique Lopes, Florentina Furtunescu, Diogo Franco, Anca Rapcea, Mihai Stanca, Alina Tănase, Anca Coliţă. (2021) Real-World Evidence: The Low Validity of Temperature Screening for COVID-19 Triage. Frontiers in Public Health 9.
- Kerem Kökoğlu, Nezaket Tektaş, Fidan Elif Baktir-Okcesiz, Mehmet İlhan Şahin. (2021) Mild and moderate COVID-19 disease does not affect hearing function permanently: a cross-sectional study ınvolving young and middle-aged healthcare givers. European Archives of Oto-Rhino-Laryngology 27.
- Muhammad Hamdan Gul, Zin Mar Htun & Asad Inayat (2021) Role of fever and ambient temperature in COVID-19, Expert Review of Respiratory Medicine, 15:2, 171-173, DOI: 10.1080/17476348.2020.1816172