LOUISVILLE, Ky. (WDRB) -- A new version of COVID-19 — an omicron sub-variant — is quickly becoming dominant strain of the virus in the United States.

During December, the percentage of new COVID-19 cases in the U.S. went from 4% to 41%, and health officials have expressed some concern.

This is new, so scientists, doctors and community leaders are learning about it as it becomes a bigger problem. Doctors said this new variant is more contagious than the last version of omicron, and Kentucky Gov. Andy Beshear said his team is keeping an eye on it.

"We don't know yet whether it will cause more or less serious disease, if it will be the same, rougher or milder," Beshear said during a news conference Thursday. "Let's all pray that it's milder. So it's important that folks who have not gotten their newest booster to go get it."

Data from the Centers for Disease Control and Prevention show less than 12% of Kentuckians five years and older have received the latest booster. But at this moment, COVID-19 levels in Kentucky are better than they were a week ago.

Beshear also gave an update Thursday on other sicknesses impacting kids. The death toll from the flu remains the same as last week: eight Kentucky children have died.

RSV cases continue to go down.

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