By Lisha Appukuttan
SARS corona virus (SARS-CoV) virus identified in 2003, is a large family of virus causing common cold to Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS). Scientists first identified a human corona virus in 1965. In early 2020, after the outbreak of the disease in China, the World Health Organization (WHO) discovered SARS-CoV-2 as a new type of virus. Any updates regarding the Severe Acute Respiratory Syndrome Corona virus-2 (SARS-CoV-2) are given high priority not only because it is contagious but also due to the profound epidemiological sustenance.
A study conducted by the CSIRO- Australia on the survival and persistence of SARS-CoV-2 reports the viability of virus for at least 28 days in cold temperatures. The research conducted to study the survival and persistence of SARS-Cov-2 on different surfaces like cotton, glass, steel, paper, plastic at 40 degree Celsius, 30 degree Celsius and 20 degree Celsius bring out the fact that the virus can survive longer on smooth surfaces and cold temperatures. The study also says that the protein and fluids in the body are also potential sources of viral contamination and therefore warns the viral contamination possibilities in meat processing units and cold storage. The study clearly asserts the need for frequent washing of hands, maintaining respiratory hygiene, cleaning of the surfaces frequently with alcohol-based sanitizers or disinfectants, wearing masks and social distancing as per WHO guidelines.
Who and How was the study conducted?
The research was conducted by the CSIRO-Australia, Australia’s National Science Agency, in partnership with the Australian Department of Defence, in collaboration with 5 national Research and Development (5RD) council, which have representatives from UK, USA, Canada, New Zealand and Australia. The research was undertaken at the Australian Centre for Disease Preparedness (ACDP) in Geelong, Victoria. The study “The effect of temperature of SARS-Cov-2 on common surfaces” was published in the Virology journal on October 11, 2020.
The main objective of the study was to find the behaviour of the virus on different surfaces which are commonly used by human and persistence of the virus in different temperatures on these surfaces. The research involved drying virus in an artificial mucus on different surfaces, at concentrations similar to viral load of infected patients. The lab condition was maintained in a state of darkness to eliminate any possible Ultra Violet light contamination, as it is already proved that UV rays or exposure to direct sunlight kills the virus. The three different temperature conditions of each substances were also maintained. The virus from these surfaces were re-isolated after a month.
The findings of the study can be briefed as follows.
|At 40 degree Celsius||Cotton||Less than 16 hours|
|Glass, Steel, Paper and polymer bank notes||24 hours|
|At 30 degree Celsius||Cotton, Vinyl||3 days|
|Glass, Steel, polymer bank notes||7 days|
|Paper banknotes||21 days|
|At 20 degree Celsius||Cotton||14 days|
|Glass, Steel, Polymer and Paper Banknotes, Vinyl||At least 28 days|
At 40 degree Celsius, the virus survived on cotton for less than 16 hours, on smooth non porous surfaces such as glass, stainless steel for 24 hours and on vinyl or plastic for 48 hours. At 30 degree Celsius, it survived for 3 days, on glass, steel, and vinyl for 7 days and on paper banknotes for 21 days. At 20 degree Celsius, virus survived longer as much as 14 days and on as glass, stainless steel, plastic and paper bank notes for at least 28 days.
|The virus survived longer at low temperatures and smooth non porous surfaces such as glass, stainless steel, plastic for about 28 days compared to nonporous complex substances such as cotton.|
|Proteins and fats in body fluids can also significantly increase the survival time of the virus.|
The study also addresses the survival, persistence and spread of the virus in meat processing facilities with high protein and fat contamination and cold environments. Thousands of workers have tested positive at meat processing factories and abattoirs around the world. The CSIRO researchers also say their findings support previous research suggesting the virus can survive on fresh and frozen food. Other reasons previously suggested include closed working conditions, cold and damp environments and the need to shout over noisy machinery.
The virus survivability and virulence depend on the type of the virus, quantity, the surfaces, environmental conditions and how the virus was deposited that is by touch or it was deposited by droplet emission, Professor Trevor Drew, Director of ACDP said. (Eurekalert)
Disagreements with the study
The data by CSIRO Australia shows the persistence of virus a lot higher than what we have known previously. One fact to be kept in mind was that the study was conducted in strict lab, viral friendly conditions where the virus was not exposed to sunlight/UV rays. But in daily life one way or another we are exposed to sunlight, but the study does remind us the need to sanitize and clean our hands and surfaces frequently, and also to expose the contaminated substances to direct sunlight.
But WHO clearly states that exposing yourself to the sun or temperatures higher than 25°C DOES NOT protect you from COVID-19. The infection can transmit no matter how sunny or hot the weather is, as counties with hot weather have also reported cases of COVID-19. Also, the normal human body temperature remains around 36.5°C to 37°C, regardless of the external temperature or weather. The most effective way to protect yourself against the new coronavirus is by frequently cleaning your hands with alcohol-based hand rub or washing them with soap and water and maintaining respiratory hygiene.
Gerchman and et.al (2020) studied the sensitivity of human Coronavirus (HCoV-OC43 used as SARS-CoV-2 surrogate) to UV LED and found that it was wavelength dependent with 267 nm ~ 279 nm > 286 nm > 297 nm. The results suggested that UV LED with peak emission at ~286 nm could serve as an effective tool in the fight against human Coronaviruses. Although UV radiation has been proved to kill Corona virus, it is not recommended to expose hands and body to Ultra-violet (UV) lamps as UV radiation can cause skin irritation and damage your eyes.
In addition, the CSIR research was conducted on artificial mucus. Prof Ron Eccles, former director Common Cold Centre at Cardiff University, differ from the findings of CSIR on basis that fresh mucus is a hostile environment for viruses as it contains lots of white blood cells that produce enzymes to destroy viruses and can also contain antibodies and other chemicals to neutralise viruses. Corona virus can only survive for a few hours in saliva or mucus. “Viruses are spread on surfaces from mucus in coughs and sneezes and dirty fingers and this study did not use fresh human mucus as a vehicle to spread the virus,” he said. (BBC News)
What were the previous findings?
The previous knowledge about the persistence of SARS-Cov-2 listed the survival ability from few hours to 4 days. But still ascertains the need of hand hygiene, social distancing and cleaning of surfaces frequently to avoid cross contamination. The study by Van Doremalan and et.al (2020) found that both the SARS-CoV and SARS-Cov-2 remain viable in aerosols for about 3 hours. Both the strains are more stable and persistent on soft non porous substances.
|Plastic, Stainless steel||72 hours||72 hours|
|Copper||4 hours||8 hours|
|Cardboard||24 hours||8 hours|
|Glass||84 hours||96 hours|
Duan SM and et.al, (2003) a member of SARS Research team, in their research on “Stability of SARS coronavirus in human specimens and environment and its sensitivity to heating and UV irradiation” found that SARS coronavirus in the testing condition could survive in serum, in 1:20 diluted sputum and in faeces for at least 96 h, whereas it could remain alive in urine for at least 72 h with a low level of infectivity. The virus was stable at 4 degree Celsius, and survived in room temperature (20 degree Celsius) and 37 degree Celsius for about 2 hours. The study also reports that at 90minutes exposure at 56 degree Celsius, 60 minutes exposure at 67 degree Celsius, 30 minutes exposure at 75 degree Celsius, the virus was converted to non- virulent form.
Most viruses from the respiratory tract, such as coronaviruses, influenza, SARS-CoV, or rhinovirus, can persist on surfaces for a few days. Persistence time on inanimate surfaces varied from minutes to up to one month, depending on the environmental conditions. Absorbent materials like cotton are safer than unabsorbent materials for protection from virus infection. The risk of transmission via touching contaminated paper is low. (Ren, 20220).
What is the normal mode of transmission?
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly contagious virus that can transmit through respiratory droplets, aerosols, or contacts. Frequent touching of contaminated surfaces in public areas is therefore a potential route of SARS-CoV-2 transmission. The inanimate surfaces have often been described as a source of nosocomial infections. The common mode of transmission also includes self-inoculation of virus to the nasal mucosa and conjunctiva with contaminated hands. (Judson and Munster, 2019). Besides the recent studies in China found that faecal contamination caused by the infected person spreads the SARS-CoV-2 after they detected live infectious agents in patient’s stools (Wang et. Al. 2020). The WHO has intimated that certain hospital procedures would also generate aerosols under specific circumstances: endotracheal intubation, bronchoscopy, open suctioning, administration of nebulized treatment, manual ventilation before intubation, turning the patient to the prone position, disconnecting the patient from the ventilator, non-invasive positive-pressure ventilation, tracheostomy, and cardiopulmonary resuscitation (WHO, 2020).
The study by Papineni and Rosenthal (1997 ) says that the highest aerosol densities were generated during coughing (virus particles few hundred to thousand) and sneezing ( virus particles few hundred thousand to few millions )and the lowest from normal nasal breathing (none to few), of which exhaled breath (few to few hundred) would be more responsible in transmitting the viruses (size of the order of 0.1 μm) when compared with transmitting the bacteria (> 1 μm). Heavy droplets will be heavy to remain in the air and fall on nearby floor or surfaces. Fomites collect droplets contaminated with virus and act as potent source of cross infection. The bioaerosols with relatively smaller aerodynamic diameter are capable of infecting people as the virus encapsulated in saliva get evaporated and these evaporated residues linger in the air for longer periods (Morawska, 2006). SARS-CoV-2 is found to be more contagious and have more epidemiological sustenance because of the high viral loads in the upper respiratory tract and the capability of the persons infected to shed viral particles and transmit to more persons while remaining asymptomatic. (Bai et.al 2020; Zon et.al 2020).
How can we survive along with Corona pandemic?
The World Health Organization lists a number of precautions you can take to avoid getting infected. WHO asserts that the best way to protect ourselves against the new corona virus is to keep at least 1 meter distance from others, washing our hands frequently and thoroughly, using masks to cover nose and mouth and maintaining respiratory hygiene, use masks to cover nose and mouth. It is also beneficial for your general health to maintain a balanced diet, stay well hydrated, exercise regularly and sleep well. It also advised to take micro-nutrients, such as vitamins D and C and zinc, as they are critical for a well-functioning immune system and play a vital role in promoting health and nutritional well-being. Garlic is a healthy food that may have some antimicrobial properties. However, there is no evidence from the current outbreak that eating garlic or other foods has protected people from the new corona virus.
The facts for and against the results regarding the persistence and viability of SARS-CoV-2 establishes that the viral viability increases with low temperatures on soft, smooth non porous substances for at least 28 days, in controlled viral friendly conditions. In the same conditions the Influenza virus survived only for 17 days. However, the behavior, virulence and persistence of the virus in the normal body temperature, environmental conditions and human saliva may vary. The previously reported facts suggest that the virus is sensitive to high temperatures and UV light, which can be used as potent tools to eradicate the virus from contaminated inanimate surfaces. But as the mode of transmission still being aerosols, droplets, self-inoculation to nasal and conjunctiva mucosa, faeces, hospital procedures and fomites the practical and possible way to prevent being infected is using three layered masks, social distancing, maintaining hand hygiene, cleaning of possible contaminated surfaces frequently, disinfecting plastic food packages etc. To prevent self-inoculation the best advisable way is to avoid touching face with contaminated hands and use, clean and dispose masks properly as per WHO guidelines.
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