US Senator Dianne Feinstein in hospital with shingles

California Democratic Senator Dianne Feinstein has been admitted to hospital in San Francisco to be treated for shingles.

Mrs Feinstein, 89, was diagnosed with the virus, which causes a painful rash, in February and is expected to make a full recovery, she said in a statement.

Shingles often develops in older adults who have had chicken pox. The rash can linger and cause damaging nerve pain.

Mrs Feinstein said last month that she would not seek another term in office.

Shingles is not typically life-threatening, according to medical experts.

Mrs Feinstein has been in California since late February and has missed a dozen votes and two committee hearings since her illness began, her spokesman told the San Francisco Chronicle.

On Tuesday, her office had announced that she would remain in California because she was “dealing with a health matter”.

“I was diagnosed over the February recess with a case of the shingles,” the senator said in a statement provided to BBC News on Thursday.

She added that she expects to make a “full recovery” and “hope to return to the Senate later this month”.

Mrs Feinstein, who was first elected in 1992, said last month that she would not seek re-election in 2024.

So far, three California members of the House of Representatives have announced bids to replace her.

Mrs Feinstein is not the only Democrat in the Senate who has been kept away from work due to health issues in recent weeks.

Senator John Fetterman has been undergoing treatment in hospital for clinical depression.

Senator Bob Casey had prostate cancer surgery last month but has since returned to work.

Democrats hold a narrow 51-49 lead in the chamber, meaning that the lack of senators has hobbled their ability to pass votes.

Twice this week US Vice President Kamala Harris has had to travel to the Capitol to exercise her ability to cast tie-breaking votes.