As the new coronavirus (SARS-CoV-2) expands around the world, scientists are beginning to understand the pathogen’s ability to survive and infectious power outside of the human body.
The WHO has warned that a person can contract the virus by sucking in droplets of secretions that an infected patient expels when coughing or sneezing, and by putting their hands to their faces after touching certain surfaces where the virus has fallen.
Now a new study published in the New England Journal of Medicine on Tuesday sheds more light on how long SARS-CoV-2 can stay active in secretions and on each of these surfaces.
The virus can maintain its infectious power for hours and even days, depending on the material in which it is found, according to the results of research carried out by the National Institute of Allergy and Infectious Diseases (NIAID) of the United States, the Control Centers and Disease Prevention (CDC) from the USA, the University of California at Los Angeles and Princeton University.
To assess the survival of SARS-CoV-2 in cough and sneeze secretions, the study authors recreated droplets of these substances from an infected person in their laboratories.
The experiment showed that a small percentage of the virus can remain active in secretions for up to three hours. And every time someone coughs, it can produce up to 3,000 droplets of secretions, according to the 2009 WHO study.
Scientists also measured the resistance of SARS-CoV-2 on materials such as stainless steel, plastic, cardboard, and copper.
In stainless steel and plastic, a percentage of the virus survived and retained its infectious capacity for up to three days.
These findings suggest that the virus could remain this amount of time on laminated or laminated door handles, countertops (or knobs), and other hard surfaces.
But there are options to remove it. A study published in the Journal of Hospital Infection in March shows that coronaviruses “can be effectively deactivated by disinfecting surfaces with 62-71% ethanol, 0.5% hydrogen peroxide (hydrogen peroxide), or sodium hypochlorite (household bleach) by 0.1% in 1 minute ”.
The survival of SARS-CoV-2 in other materials was lower than in steel and plastic.
The virus survived only 24 hours on cardboard surfaces and just four hours on copper.
“The natural absorbent fibers in a cardboard can cause the virus to dry faster than plastic and metal,” said Vincent Munster, head of the Virus Ecology section at Rocky Mountain Laboratories and one of those who led the I study BBC Future’s, Richard Gray.
It is not yet clear how long the virus can survive on clothing and other more difficult to disinfect surfaces.
Temperature and humidity can also affect how long the virus survives outside of the human body.
“[We are] currently conducting follow-up experiments to investigate the effect of temperature and humidity in more detail,” Munster told BBC Future.
It is not yet known exactly how many cases of covid-19 result from contact with contaminated surfaces, but experts advise caution.
The U.S. Centers for Disease Control and Prevention, WHO and other health authorities emphasize that both hand washing and daily disinfecting frequently touched surfaces are key to preventing the spread of covid-19.
Experts also recommend covering your mouth with the crease of your elbow when you cough or sneeze, or use a disposable tissue and dispose of it in a closed trash container.
Munster also highlights the importance of these hygiene measures given the virus’s ability to resist for so long. “This virus has the potential to be transmitted through various routes,” says the expert.
The study authors compared the survival of the new coronavirus with that of SARS-CoV-1, the “most similar” in the coronavirus family and which causes Severe Acute Respiratory Syndrome (SARS).
This disease affected more than 8,000 people in 26 countries and caused nearly 800 deaths in 2003, over eight months.
The survival rate of both viruses on different surfaces was similar, the study says. So why is the spread of covid-19 being so much higher?
The differences may be due to factors such as “high viral loads (from the new coronavirus)” in the airways and “the possibility that people infected with SARS-CoV-2 transmit the virus while asymptomatic,” say the authors of the investigation.
“This would make the disease control measures that were effective against SARS-CoV-1 less effective against its successor,” warns the US National Institute of Health. in a statement about the survival study, released this Tuesday.