Queen Elizabeth II is currently suffering from COVID-19, joining nearly 19 million of her British subjects who have contracted the virus during the pandemic.
Buckingham Palace insists the 95-year-old monarch is only experiencing mild symptoms, and will continue to carry out light duties while she recovers.
But this is not the first time an infectious disease has breached the palace walls.
From the bubonic plague of the 14th century to the influenza outbreak of 1889, royal family members have not been spared the ravages of disease outbreaks.
In some cases, pandemics have changed the course of history, claiming the lives of monarchs and heirs and shifting the royal line of succession.
The Black Death kills two queens
The bubonic plague remains one of the deadliest diseases in human history.
From 1347, the bacteria that can leap from animals to humans swept through vast swathes of the world, killing as many as 25 million people in four years.
The plague, which causes painful, swollen lymph nodes and septic shock, did not discriminate when it came to the royal family.
King Edward III lost his 14-year-old daughter Joan, who contracted the deadly disease when she was on her way to Spain to get married.
While the worst of the bubonic plague outbreak subsided by the early 1350s, the disease still stalked Europe for decades to come.
In 1394, Richard II lost his wife Queen Anne of Bohemia to the plague, leaving the king so devastated, he demolished the palace in which she had died.
In the years after her death, the grief-stricken king behaved recklessly and tyrannically towards his subjects, and he was finally deposed by his cousin Henry IV in 1399.
After he starved to death in the Tower of London, the new king denied Richard his final wish to be buried beside his late wife.
'Death possessed every joint of me'
But no disease outbreak had a more profound impact on the crown than smallpox.
The virus of mysterious origins is highly contagious, disfiguring and deadly, causing a rash of blisters or pustules on the skin.
In 1552, King Edward VI — the only son of Henry VIII — fell ill with measles and smallpox at the age of 14.
Though he recovered quickly, he succumbed to tuberculosis just a year later, which was blamed on his poor immune system.
With no other male heirs, the crown went first to his half-sister Mary and then Queen Elizabeth I in 1558.
As smallpox raged across Europe, Elizabeth I became dangerously ill with the disease at the age of 29.
"Death possessed every joint of me," she is believed to have told a parliamentary delegation in 1562.
She eventually recovered from smallpox, but her face was left scarred by the disease, which she covered with white lead-based makeup.
Elizabeth I was reportedly so distraught by her appearance that she demanded all mirrors be removed from her living quarters.
Influenza and the lost king
If not for the influenza pandemic of the 19th century, someone other than Queen Elizabeth II would be sitting on the throne right now.
In 1889, an outbreak of what was called Russian flu killed about 1 million people — including the future king of England, Albert Victor.
Queen Victoria's handsome grandson was just 28 years old and weeks away from his much-anticipated wedding to his fiancee Mary when he suddenly fell ill.
His bout of influenza turned into pneumonia, and to the shock of a nation, he died a week later.
"It changed the course of history, with his younger brother becoming king," Vyki Sparkes from the Museum of London said in 2018.
Not only did George V take his brother's place on the throne, he also married his fiancee, Mary.
Together they had six children.
Among their nine grandchildren was a future queen: Elizabeth II.
COVID bursts the Queen's 'HMS Bubble'
When the COVID-19 pandemic reached the UK in early 2020, Prince Charles was still regularly attending crowded events and receptions.
It wasn't long before the future king tested positive for the virus.
After self-isolating in Scotland, Prince Charles recovered quickly.
It later emerged that his son, Prince William, contracted COVID-19 at a similar time to his father.
However, his condition was not disclosed for months to avoid alarming the UK, according to the BBC.
With both of her direct heirs exposed to the virus, every effort was made to protect the Queen.
She and her husband Prince Philip spent his final months together locked down at their favourite home, Windsor Castle.
There, they were cared for by a small staff of 22, nicknamed HMS Bubble.
When Prince Philip died last year, the royal family adhered to the UK's strict COVID protocols for funerals.
A photo of a masked Queen sitting alone at the church service is likely to be an enduring image of her reign.
The surge of the Omicron virus this year saw Prince Charles infected with COVID-19 for a second time.
As his wife Camilla, Duchess of Cornwall, also tested positive, and reports emerged of a growing cluster at Windsor Castle, it seemed the Queen's COVID-free bubble had finally burst.
But unlike her predecessors, this monarch has modern medicine on her side.
With the Queen fully vaccinated and receiving the best of care, she is expected to make a full recovery.
