WASHINGTON - Former US Secretary of State Hillary Clinton announced on Tuesday evening that she had contracted COVID-19 with mild symptoms.

"I've got some mild cold symptoms but am feeling fine," tweeted the 74-year-old, who was also the 2016 Democratic presidential nominee, adding that she had been vaccinated.

"I'm more grateful than ever for the protection vaccines can provide against serious illness," she said.

Her husband, former US President Bill Clinton, tested negative on Tuesday for the coronavirus and is "feeling fine," according to a follow-up tweet.

Bill Clinton, 75, is "quarantining until our household is fully in the clear," Hillary Clinton wrote.

The tweets came only hours after White House press secretary Jen Psaki announced a positive test result, the second for her in just a few months.

"Thanks to the vaccine, I have only experienced mild symptoms," Psaki said in a statement, adding US President Joe Biden tested negative on Tuesday via a PCR test.

Hillary Clinton and Psaki are the latest in a series of prominent US figures who have recently been infected with COVID-19, joining a list that also includes former US President Barack Obama and second gentleman Doug Emhoff, husband of US Vice President Kamala Harris.

US Senator Bob Casey from Pennsylvania also reported a COVID-19 infection on Tuesday in a breakthrough case.

"I'm grateful to be asymptomatic," Casey tweeted. "This is reminder that the pandemic is not over. Please get vaccinated and boosted."

At least 155 members of the US House of Representatives and the Senate have been diagnosed with COVID-19, one of whom subsequently died of COVID-19, since the outbreak of the disease in the United States two years ago, according to a tracking website.

The United States has reported more than 79 million COVID-19 cases and 972,000 deaths, both the highest in the world, according to Johns Hopkins University data.

Public health experts have warned that the United States may see another rise in COVID-19 cases in the next few weeks, as the new Omicron subvariant continues to spread across the nation while restrictions are being lifted in states and cities.