Researchers in Japan have found that the coronavirus can survive on human skin for up to nine hours, offering further proof that regular handwashing can curb the spread of Covid-19, according to a study published in the journal Clinical Infectious Diseases.

Scientists from the Kyoto Prefectural University of Medicine compared the survival times of the coronavirus and influenza A (flu) virus. They found that the pathogen that causes the flu survives on human skin for about 1.8 hours by comparison.

“The nine-hour survival of SARS-CoV-2 [the virus strain that causes Covid-19] on human skin may increase the risk of contact transmission in comparison with IAV [influenza A virus], thus accelerating the pandemic,” it said. “Proper hand hygiene is important to prevent the spread of SARS-CoV-2 infections.”

The research team tested skin collected from autopsy specimens no more than one day after the patient’s death. Both the coronavirus and the flu virus are inactivated within 15 seconds by applying ethanol, which is used in hand sanitisers, the study showed.

Researchers also mixed samples with mucus to mimic a sneeze or cough. The coronavirus lasted 11.09 hours, while the influenza A lasted 1.69 hours, the study said. Both the Covid-19 virus and the influenza A virus were “completely inactivated” within 15 seconds of applying ethanol, it added.

Various scientists have time and again spoken about the viral transmission of the coronavirus. Earlier this month, a study published by Commonwealth Scientific and Industrial Research Organisation researchers suggested SARS-CoV-2, the virus that causes Covid-19, can survive up to 28 days on common surfaces.

The scientists found that at 20 degrees Celsius, SARS-CoV-2 was “extremely robust” on smooth surfaces like mobile phone screens, surviving for 28 days on glass, steel and plastic banknotes. At 30 degrees Celsius, the survival rate dropped to seven days and plunged to just 24 hours at 40 degrees Celsius.

In comparison, the virus survived for shorter periods on porous surfaces such as cotton – up to 14 days at the lowest temperatures and less than 16 hours at the highest – the researchers said.

In March, the National Institutes of Health published a study saying that the virus can last up to four hours on copper, 24 hours on cardboard, and 72 hours on stainless steel. Besides this, the study had said the virus can last for about three hours in the air.

In September, the United States Centers for Disease Control and Prevention updated its guidelines on the coronavirus to say that the infection can spread through aerosols, which are produced even when a person breathes.

In July, 239 scientists wrote to the World Health Organization and other public health institutes, urging them to be more open about the possibility that people could get infected by droplets that were floating in the air.

Globally, the coronavirus has infected more than 3.96 crore people and killed 11,08,607, according to Johns Hopkins University. The worldwide recoveries have crossed 2.72 crore.