Omicron transmissibility and virulence: What do these terms mean?

Cases of COVID-19 caused by the omicron variant have been detected in the U.S., according to the Centers for Disease Control and Prevention. Mayo Clinic experts are actively monitoring the new variant to better understand how it behaves.

Gregory Poland, M.D., head of Mayo Clinic's Vaccine Research Group, is among the researchers around the world following the new variant. Some of the biggest questions about omicron are how easy it spreads and the severity of illness it causes.

"There are a number of aspects or words that we use to describe the behavior of a virus. One is infectivity or transmissibility. Let's say I was infected. What's the opportunity or the risk that I could spread that to you, an unimmunized and uninfected person? Virulence refers to the likelihood of disease that would be caused by that infection," says Dr. Poland.

Research to better understand omicron's transmissibility and virulence is happening now, and Dr. Poland says it will take several weeks.

"The way I've put it to people is this way: we've heard a fire alarm and we see smoke. What we have to do now is go into the building — that takes us two or three weeks — open the door and find out (if this is) a small fire that will be contained by boosters or is this a raging, about to be out of control, fire? It could be either and anything in between those possibilities at this point."

In the meantime, Dr. Poland says everyone already has the "secret" to protect themselves.

"I will tell you the secret to protecting yourself from omicron. And it's really pretty easy. It's the advice we have consistently given here at Mayo Clinic and true at any medical center. Wear a mask when you're indoors, be immunized and be boosted," says Dr. Poland.

Information in this post was accurate at the time of its posting. Due to the fluid nature of the COVID-19 pandemic, scientific understanding, along with guidelines and recommendations, may have changed since the original publication date.