The novel coronavirus disease 2019 (COVID-19) is a worldwide pandemic despite massive preventive measures taken globally and locally, including travel restrictions, social distancing, and quarantines. SARS-CoV-2 (severe acute respiratory syndrome coronavirus2) first appeared in Wuhan; China took only three months to spread over 200 countries infecting approximately 2.4 million people and causing 150,000 deaths. This infection at an early stage presents with seasonal flu-like symptoms to severe illness and high mortality rates. Therefore, the researchers thought that high-temperature weather could drop the spread of coronavirus infection.
Can High Temperatures Kill The Coronavirus?
Few studies and researchers have stated that coronavirus survives for shorter periods at high temperatures than in cool or dry environments. However, no evidence or data shows the virus's temperature-based inactivation. Instead, the temperature is based on the material's surface, the environment, etc
Some facts and literature suggest that certain temperatures and exposure durations are required to inactivate SARS-CoV-2.
What Are The Recommendations For The Thermal Destruction Of Coronavirus?
Temperature above 75 degrees for three minutes.
Temperature above 65 degrees for five minutes.
Temperature above 60 degrees for 20 minutes.
These recommendations are based on a conservative approach lowered by log five to seven or below the detectable limit.
Due to the seriousness of coronavirus infection, a safety factor is suggested by increasing the above-listed temperatures by 10 degrees. Extensive research has confirmed the coronavirus’ sensitivity to thermal destruction is strongly linked to temperatures for living cells. Also, a slight increase in temperature causes a significant increase in the death rate. For example: for a mammalian cell, pathogens like bacteria, viruses, or parasites, the death rates increase rapidly with the increase in temperatures.
The temperatures experienced by the viruses during the heating will not necessarily match the applied heat. Therefore, thermal inertia causes a heating lag that depends on the media used partially.
These recommendations are based on WHO (World Health Organization) guidelines that report a four-log reduction of coronavirus at 56 degrees Celsius with 15 minutes of exposure and is consistent in killing other infectious agents. These recommended temperatures are hotter than heat encountered at residential clothes dryers, washing machines, dishwashers, and hot water.
Can Summer Heat Kill Coronavirus?
The pandemic outbreak started in December 2019, and various statements were released about the virus survival during the summer as the seasonal flu is lower in summer than in winter. Researchers and the general public also thought that the coronavirus infection rate might drop.
Few studies showed that the viability of coronavirus variants was decreased with high temperature and low humidity environments. This study also suggested that tropical countries have a low risk of developing SARS (severe acute respiratory syndrome) coronavirus infection when compared with cold countries. Thus, the study reports that the summer may reduce SARS-CoV-2 disease or transmission rate compared to winter.
In addition, various studies have also documented that a cold environment increases the susceptibility to viral infection because of the suppression of immune responses. Hence, people living in cold climates are at additional risk for COVID-19 severity.
Does The Environment Affect Coronavirus Infection?
The present evidence reveals that coronavirus severity is higher in patients with pre-existing medical conditions such as diabetes, hypertension, cancer, obesity, and heart and kidney diseases. In addition, many reports suggest that the virus enters the body through the endocytosis process in which the viral spike proteins interact with cell surface receptor angiotensin-converting enzyme 2 (ACE-2) proteins present over epithelial cells of the respiratory tract, lungs, and other tissues.
Therefore, the sensitivity of coronavirus to temperature may vary from one mutant type to others. In addition, the efficacy of infection varies in age, race, ethnicity, and gender. Also, infectivity depends on other factors such as hygiene practices, population crowding, and lifestyle.
Is It Possible To Inactivate Coronavirus By Heat?
A Medline search was conducted in March 2020, stating “coronavirus heat inactivation,” and results were extracted with original data on human SARS and MERS, zoonotic coronaviruses, mouse Hepatitis virus, and porcine epidemic diarrhea virus and their inactivation by various temperatures for thermal disinfection.
A thermal inactivation at 60 degrees Celsius for 15 minutes and 80 degrees Celsius for one minute effectively reduced coronavirus strongly and its infectivity by four logs. The effectiveness of heat by thermal aggregation of SARS-CoV-2 membrane protein showed that the nucleocapsid is completely denatured in ten minutes at 55 degrees Celsius. Thus the healthcare providers got an idea of what parameter thermal disinfection is effective. Inactivation of the virus by heat is commonly achieved through sterilization and pasteurization techniques which are used in various industries to ensure safety. Heat-based methods for virus inactivation involve direct heat application to surfaces or using high-temperature treatments in controlled environments like laboratories or industrial settings.
What Is The Effect Of Heat Treatment On Coronavirus Infectivity?
Heat inactivates the virus by denaturing the secondary protein structures, thereby altering the virion proteins' conformation involved in attachment and replication within a host cell.
The ability of heat to inactivate the coronavirus is found to be at 56 degrees Celsius for 20 minutes. However, a certain amount of the virus remained stable. With an increase in temperature to 65 degrees Celsius, most virus was inactivated when incubated for more than four minutes.
Thus, the virus was inactivated entirely at 56 and 65 degrees Celsius at 60 minutes and 75 degrees Celsius at 45 minutes. Altogether, the virus inactivation through pasteurization can also be effective.
The efficacy of coronavirus inactivation by thermal or heat treatment helps improve laboratory safety disinfection of objects, instruments, and masks.
High temperatures can kill the coronavirus by inactivating and denaturing the viral protein. Certain recommendations are given at which the virus can be inactivated completely. Summers or tropical countries are at lower risk of developing coronavirus infection than winter or cold countries. The reports suggest that coronavirus is severe in people with underlying medical conditions, age, race, ethnicity, gender, etc., and is not entirely dependent on environmental factors. Heat can inactivate the virus completely but cannot stop infection of coronavirus.