No trace of virus on paper after 3 hours
STUDY CONDUCTED BY INCUBATING SARS-COV-2 IN A VIRUS TRANSPORT MEDIUM FOR 14 DAYS AND THEN TESTING
ITS INFECTIVITY ON VARIOUS SURFACES
NEW DELHI: SARS-COV-2 doesn’t survive on print or tissue paper for more than 3 hours, a new study by the School of Public Health at the University of Hong Kong has found.
The study, which is yet to be published also found that the virus doesn’t remain infectious on cloth or treated wood after a day. Strangely, a significant level of infectious virus could be detected from the outer layer of a surgical mask even 7 days after the virus was introduced to the surface during the study.
Sars-cov-2 is very stable on smooth surfaces and continues to be infectious for days together. Infectious virus was not found on glass or bank notes treated with the virus after day 4 and after day 7 on stainless steel and plastic.
This can however be countered with use of disinfectants. No infectious virus could be detected 5 minutes after disinfecting a surface with soap and water. “Overall, Sars-cov-2 can be highly stable in a favourable environment, but it is also susceptible to standard disinfection methods,” the study published in its preprint version in Medrxiv said.
Scientists conducted this study by incubating Sars-cov-2 in a virus transport medium for 14 days and then tested its infectivity on various surfaces. The virus is stable in lower temperatures but sensitive to heat, the study revealed. At 4 degree C for example it was found to be most stable but when incubation temperature was increased to 70 degrees C, the virus was inactivated in 5 minutes.
“Its best to disinfect all surfaces during an outbreak like this. Hypochlorite is best for disinfection but because it may not be available to common people at the moment just use any disinfectant or soap and water. I have been using soap and water at my house. The hospitals and health care workers have access to hypochlorite. I am sure surfaces are being disinfected regularly at hospitals,” said Dr Shobha Broor, former head of microbiology at AIIMS).
In a correspondence published on ‘Aerosol and Surface Stability of Sars-cov-2 as Compared with Sars-cov-1’ in The New England Journal of Medicine, scientists said that Sars-cov-2 was more stable on plastic and stainless steel than on copper and cardboard and viable virus could detected up to 72 hours after application on them.
The University of Hong Kong study also revealed SARS-COV-2 is extremely stable in a widerange of ph values at room temperature. “This means that washing anything in water will not help unless its washed in hot water or with a disinfectant. The key takeaway from this study is that bleach and ethanol are extremely effective in inactivating the virus. We knew this always but the study reinforces that our current understanding is correct,” said Amit Singh, associate professor, Centre for Infectious Disease Research, Indian Institute of Science, Bengaluru.
The World Health Organisation has already addressed the question whether it is safe to receive a package. WHO said: “The likelihood of an infected person contaminating commercial goods is low and the risk of catching the virus that causes COVID-19 from a package that has been moved, travelled, and exposed to different conditions and temperature is also low.”
“There is a study from 2011 on the H1N1 virus which led to the 2009 outbreak which says that the virus does not survive on porous surfaces like paper, cloth or tissue for very long. But it can stay up to 48 hours on surfaces like steel, plastic, glass, aluminium, copper etc. This is simply because the protein envelope of the virus disintegrates easily in dry, porous surfaces. The virus may last only for about 4 hours on such surfaces. This is based on evidence from the H1N1 flu epidemic,” said Dr Amit Singh, associate professor, Centre for Infectious Disease Research at the Indian Institute of Science (IISC) had told HT on March 24 after reports that people are not availing newspapers out of the fear of contracting the infection.