Since then, his wife Camilla has also tested positive, while reports claim the Queen is being monitored after being in contact with Charles two days before his positive test.
It's understood that the Queen is not displaying symptoms and Palace sources say they won't be providing commentary on her health.
She returned to work on February 15 via video link, holding audiences from Windsor Castle with incoming ambassadors from Estonia and Spain. The meeting marked the first time the Queen had been seen since Camilla's positive test was announced.
And the head of the Firm attracted quite the response on social media, with one fan writing that they were "praying" for her health.
"Praying for Her Majesty's health. I'm so happy to see she's up and about and not feeling poorly. Covid for any senior citizen can be dangerous," they wrote online.
The exact date when the Queen will resume in-person engagements is not currently known.
She began her Platinum Jubilee celebrations with a reception at Sandringham House and considering the incredible number of events planned for June, the Queen will no doubt be eager to get out and about once again as the milestone occasion draws near.
