Guidelines from the Centers for Disease Control and Prevention that make the rounds this week on the Internet clarify what we know about the transmission of coronavirus.
The virus does not spread easily through contaminated surfaces, according to C.D.C. For those who were worried about wiping out food bags or disinfecting mail packages, news headlines that highlighted this guidance in recent days may have led to some relief.
The coronavirus is believed to be mainly spread from one person to another, usually through drops when an infected person sneezes, coughs or speaks up close – even if the person does not show symptoms.
“The virus that causes Covid-19 spreads very easily and sustainably between humans,” says C.D.C. says on his website. “Information from the ongoing Covid-19 pandemic indicates that this virus is spreading more effectively than influenza, but not as effectively as measles, which is highly contagious.”
The website also says that people can get infected by “touching a surface or object that has the virus on it and then touching their own mouth, nose or possibly their eyes.” But they are “not believed to be the main way in which the virus spreads.”
The format for C.D.C. the site changed slightly this month, but the language of surfaces remained the same. It seems to have been placed under a new sub-heading – “The virus does not spread easily in other ways” – on May 11, and more information on the difficulty of catching the virus from animals was added.
Kristen Nordlund, spokeswoman for the agency, told us The Washington Post said the audits followed an internal review and were the product of “usability testing.”
“Our transmission language has not changed,” Nordlund said. “Covid-19 is spread primarily through close contact from person to person.”
Experts at C.D.C. and elsewhere is still learning about the new coronavirus.
There are questions about how the density of virus particles can affect transmission rates. Researchers do not yet know if all the speech, cough and neon drops that carry the particles are equally contagious or whether a certain amount of virus must be transmitted in order for a person to become ill by inhaling it. A study last week found that talking alone can launch thousands of drops into the air, and that they can remain suspended for eight to 14 minutes.
It seems that the virus spreads most easily when people are in close contact with each other – for example, in a conversation – or gather in poorly ventilated spaces, said Linsey Marr, aerosol scientist at Virginia Tech.
She said that for a person to catch the virus from the surface, it seems like some things should happen. First, the virus must be transmitted to the surface in sufficient quantities. Then it must survive on that surface until it was touched by someone else. And even if it was eventually transferred to, say, a person’s finger, it would then have to survive on the skin until the person accidentally touched an eye or mouth.
“There are just a lot more conditions that need to be met in order for the transfer to take place through the touch of these items,” Dr. Marr.
And since catching coronavirus from a contaminated surface is still considered a possibility, people who prefer to wipe down bags, boxes or park benches can still do so. C.D.C. recommends that you wash your hands frequently and clean or disinfect the affected areas regularly.