Sen. Dianne Feinstein is in the hospital with a case of shingles, her office confirmed Thursday afternoon.

Feinstein's office said earlier on Thursday that the senior senator was in California dealing with a "health matter" but hoped to return soon to Washington, D.C.

"I was diagnosed over the February recess with a case of shingles," Feinstein relayed through a spokesperson. "I have been hospitalized and am receiving treatment in San Francisco and expect to make a full recovery. I hope to return to the Senate later this month."

Feinstein, 89, said last month that she will not seek reelection in 2024 after serving 30 years in the U.S. Senate. Feinstein is the oldest member of the Senate and the longest-serving female senator.

Reps. Adam Schiff, Barbara Lee and Katie Porter are in the running to replace Feinstein after she terms out.