What We Know About Omicron Symptoms & When You Become Contagious, According To Studies

Omicron has seemingly come out of nowhere to change the shape of the pandemic, and that includes shaking up what can be expected from a positive COVID-19 test.

Scientists and doctors are currently racing to study the variant, and while they still don't know everything, early data may offer some insight into how it works. It's also shedding some light on what people mean when they describe Omicron as "mild."

Omicron is spreading "significantly faster" than the Delta variant, according to a technical briefing released by the World Health Organization on Thursday. It can also be detected through typical testing methods.

Early data suggest a reduction in protection against the variant in those who have only had a primary vaccination series (meaning they did not receive any booster doses) or have already been infected with the coronavirus, the WHO says.

The info is based on early data from studies in hard-hit areas such as South Africa, Denmark and the United Kingdom, but it's still too early to put exact numbers on the risks, the WHO says.

But what does Omicron look like? What does it feel like? And what does it mean for you if you get it?

"Prominent" symptoms of an Omicron infection are coughing, fatigue, congestion and a runny nose, infectious disease specialist Dr. Katherine Poehling tells NBC News.

Headaches and sneezing are also common with Omicron, according to the ZOE COVID Study, an app-based pandemic research project in the U.K.

Poehling adds that one of the symptoms usually reported with COVID-19 infection — loss of taste and smell — is less common with Omicron. ZOE and a study of an outbreak in Norway also found that to be the case, although more data is needed.

In other words, an Omicron case will look a lot like a case of Delta, except your sense of smell and taste might be intact.

Once you have Omicron you can spread it to others, according to the U.S. Centers for Disease Control and Prevention. The CDC expects that anyone with an infection can spread Omicron, "even if they are vaccinated or don't have symptoms."

One study out of Hong Kong found that Omicron replicates 70 times faster in the human bronchus, which connects the windpipe to the lungs, than Delta.

Early data suggests that the risk of hospitalization is lower with Omicron than with Delta, according to the WHO brief. However, the WHO says that more data on the severity of the variant is needed.

An early U.K. study at Imperial College found that people with Omicron had a 20-25% lower chance of needing a hospital visit, and a 40-45% lower risk of spending the night at the hospital when compared to a Delta infection.

The early studies suggest that Omicron illnesses may be milder than Delta, but that doesn't mean we should take it lightly, study co-author Azra Ghani told the New York Times.

"We’re not at a place to treat this as a cold," Ghani said.

The WHO says more studies are needed to get an accurate picture of the risk of Omicron.

In the meantime, public health agencies such as the CDC have the same advice as always: get vaccinated, wear a mask and get tested if you think you've been exposed.