The head of the Centers for Disease Control and Prevention (CDC) said she believes the U.S. is “ripe” for a severe flu season this year.

“Not everybody got flu vaccinated last year, and many people did not get the flu,” CDC Director Rochelle Walensky told NBC News. “So, that makes us ripe to have potentially a severe flu season.”

Walensky also noted that flu activity is starting to increase across the country, particularly in the South and south-central portions of the country.

This is not the first time this year that health experts have warned that the country is in for a tough flu season. Outgoing chief White House medical advisor Anthony Fauci said in early September that the U.S. should prepare for a “pretty bad flu season.”

Just under half of Americans in a recent survey — 49 percent — said they plan to get the flu shot this year, while another 41 percent said they unsure or do not plan to get the flu vaccine.