Elizabeth Warren at the Capitol - Copyright 2021 The Associated Press. All rights reserved.© Copyright 2021 The Associated Press. All rights reserved.Elizabeth Warren at the Capitol

– Copyright 2021 The Associated Press. All rights reserved.Sen. Warren tweeted on Sunday: “I regularly test for Covid and while I tested negative earlier this week, today I tested positive with a breakthrough case.”

“Thankfully, I am only experiencing mild symptoms and am grateful for the protection provided against serious illness that comes from being vaccinated and boosted.”

Her positive result comes about 18 months after her brother died of coronavirus.

She tweeted: “As cases increase across the country, I urge everyone who has not already done so to get the vaccine and the booster as soon as possible together, we can save lives.”

Her exposure to the virus could potentially mean that other senators or their staff could suffer infections as well, given that Ms Warren was on the floor of the Senate in recent days for a marathon late-night session in which the upper chamber confirmed dozens of President Joe Biden’s nominees, including that of former Chicago Mayor Rahm Emanuel as ambassador to Japan.

Ms Warren’s positive diagnosis is also a sign of the continued infectiousness of the virus; she is fully vaccinated, including a booster shot, and still facing mild symptoms.

The Biden administration has been redoubling its efforts to encourage vaccinations and booster shots in recent days given the onset of the Omicron variant, which is thought to be more infectious that some previous iterations of Covid-19 while possibly resulting in milder symptoms.

Hospitals around the US are, meanwhile, reporting the same phenomenon over and over: The vast majority of hospitalisations and deaths, which continue to overwhelm healthcare systems in municipalities across the country, are among unvaccinated Americans who face a much greater risk of severe symptoms from the virus than do their vaccinated neighbors.

The US is facing a new wave of Covid-19 infections, attributed largely to the spread of the Omicron variant as well as the onset of winter weather. The country is averaging more than 125,000 new cases per day as of this weekend, and the rate of new cases is continuing to grow.

News of Ms Warren’s diagnosis comes just about 24 hours after it was reported by multiple local news outlets that an outspoken Washington state senator who opposed Covid-19 vaccine mandates had died after contracting the virus.

From news to politics, travel to sport, culture to climate – The Independent has a host of free newsletters to suit your interests. To find the stories you want to read, and more, in your inbox, click here.