SARS-CoV-2 survives on human skin for 9 hours

More than 36 million people worldwide have been infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) since the virus emerged in Wuhan, China, in late December 2019. The SARS-CoV virus -2 that causes COVID-19 disease is known to survive on skin and inanimate objects and can be easily transmitted from person to person.

Japanese researchers have now studied the survival chances of the influenza virus and SARS-CoV-2 on human skin. His study entitled “Survival of SARS-CoV-2 and the influenza virus in human skin: importance of hand hygiene in COVID-19”, is published in the latest issue of the journal. Clinical infectious diseases.

Transmission electron micrograph of a SARS-CoV-2 virus particle isolated from a patient. Image captured and enhanced in color at the NIAID Integrated Research Facility (IRF) at Fort Detrick, Maryland. Credit: NIAID

Background

The research was an attempt by researchers at the Kyoto Prefectural University of Medicine in Japan to study the stability of SARS-CoV-2 in human skin.

Since live SARS-CoV-2 cannot be used, the team first had to create a model that would allow them to experiment with applying pathogens to human skin.

Hand washing and hygiene

Several studies have shown that one of the best ways to prevent the transmission of highly infectious viruses like the novel coronavirus and the flu virus is to repeatedly wash your hands with soap and water for at least 20 seconds and disinfect your hands with hand-based disinfectants of alcohol. with at least 70 percent alcohol content.

The authors wrote that studies have shown that SARS-CoV and the Middle East respiratory syndrome coronavirus (MERS-CoV) have greater stability compared to influenza A virus (IAV).

Models to experiment with

It is unethical and dangerous for human skin to be exposed to SARS CoV-2 or highly pathogenic IAV (PR8; A / Puerto Rico / 8/1934; H1N1). Therefore, skin samples must be obtained by surgical procedures, which were found to be inappropriate. Therefore, the team gathered forensic autopsy samples of human skin obtained from the Department of Forensic Medicine at the Kyoto Prefectural University of Medicine for their experiments.

The team explained that human skin, especially the epidermis, slowly deteriorates after death compared to other organs and can be used for grafts even 24 hours after death. They collected abdominal skin samples from deceased people between the ages of 20 and 70. The duration of the autopsy was 24 hours, and these skin samples were cut into rectangles measuring about 4 × 8 cm.^two.

Viruses and the experiment

The team prepared a mixture of SARS-CoV-2 and influenza A virus (IAV) with culture medium or mucus from the upper respiratory tract. This mixture was applied to the surfaces of human skin. They then disinfected the surfaces with 80% ethanol (w / w) and checked if the viruses survived.

The team analyzed the stability of SARS-CoV-2 and compared it to that of IAV. IAV is known to be transmitted through droplets and contact transmission. Using this model, they analyzed the stability of the viruses in;

• the stainless steel surface,
• the surface of borosilicate glass,
• the polystyrene surface,
• the surface of human skin.

Then, they mixed the SARS-CoV-2 and IAV with mucus from the upper respiratory tract. They explained that these viruses tend to be transmitted through infectious bodily fluids (mucus).

Disinfection

In their experiment, they looked at the effectiveness of 80 percent (w / w) of ethanol in disinfecting human skin, which had been exposed to SARS-CoV-2 or IAV.

Results and findings

The team first validated their experimental model using IAV samples on the skin. They also evaluated the stability of SARS-CoV-2 and IAV mixed in a cell culture medium.

This was evaluated on various surfaces and the survival time of SARS-CoV-2 was found to be approximately 8 times the survival time of IAV on these surfaces, the former was found to have higher stability.

However, when tested on human skin, the viruses were rapidly inactivated compared to stainless steel, borosilicate glass, and polystyrene surfaces. SARS-CoV-2 was more stable on human skin surfaces compared to IAV.

Survival times averaged 9.04 hours compared to 1.82 hours for SARS CoV-2 and IAV, respectively. The half-lives of the viruses were 3.53 hours and 0.80 hours for SARS CoV-2 and IAV, respectively.

When mixed with mucus, stability was tested and the team observed:

• IAV was more rapidly inactivated in mucus on inanimate surfaces compared to when in cell culture medium (Dulbecco’s Modified Eagle’s Medium or DMEM)
• The stability of SARS-CoV-2 in mucus and cell medium (DMEM) was similar
• The survival times and half-life of SARS-CoV-2 in mucus were significantly longer than those of IAV in human skin.
• Survival times averaged 11.09 hours compared to 1.69 hours for SARS CoV-2 and IAV, respectively, in human skin mucus.
• Half-life times averaged 4.16 hours compared to 0.77 hours for SARS CoV-2 and IAV, respectively, in human skin mucus.
• SARS-CoV-2 and IAV in both mucus and DMEM were completely inactivated in all human skin after 15 seconds of treatment with 80 percent (w / w) ethanol.

Conclusions and repercussions

This study shows that SARS-CoV-2 could survive on human skin for up to 9 hours and therefore there is a risk of transmission by contact.

The survival of the coronavirus on the skin is significantly longer than that of the influenza virus, making its spread a more significant public health problem.

The study authors wrote, “Proper hand hygiene is important to prevent the spread of SARS-CoV-2 infections.” They found that it only takes 15 seconds of treatment with 80 percent ethanol to kill any of the viruses on human skin.