"Sending love from everyone here to everyone supporting from afar, it is hugely appreciated".
In an update published Friday, Branson wrote: "It is a traumatic time here in the British Virgin Islands". Her husband, who is still there, told her that residents and tourists are in shock. The island was wiped out.
But that number looks set to rise - and could reach as high as 26 million, the agency said.
Cuba was also hard hit by the hurricane, where central Havana neighbourhoods along the coast between the Almendares River and the harbour suffered the brunt of the flooding.
In the Leeward Islands, the first to encounter Irma's deadly winds and storm surge, residents complained they were running short on food, water and medicine.
Irma claimed at least 20 lives as it leveled islands in the Caribbean and headed toward Florida, where a massive evacuation was in progress.
Branson had said earlier his compound was built with reinforced hurricane blinds created to withstand high winds. The facility had been without power for days, he said. "The electricity infrastructure received extensive serious damage".
It came after two MPs criticised the reaction times by the government.
On Tuesday, French President Emmanuel Macron was scheduled to arrive in Saint Martin to bring aid and fend off criticism that he didn't do enough to respond to the storm's wrath. "We pre-positioned a ship in the Caribbean for the hurricane season; it wasn't by chance that [British naval vessel] Mounts Bay, a huge 16,000-tonne aid ship, with marines, with a helicopter, with pallets of aid, was already in the Caribbean".
Cluff dismissed criticism in the United Kingdom media of the British government's support for its overseas territories, where there were no evacuations despite the warnings. Dutch news outlets showed the king touring the badly damaged Princess Juliana International Airport, which was named for his grandmother.
To the west of the British Virgin Islands are the American (US) Virgin Islands consisting of Saint Croix, Saint John, and Saint Thomas as well as smaller neighbouring islands. The people there, many of whom are old friends of mine, are suffering. She shared with us what it was like enduring Irma's fury.
"I've lived through a hurricane before". I am lost for words at this point.
"But I've absolutely no doubt that we can face up to the challenge, we can deliver the help that those islanders need, we are seeing some signs of improvement, things are getting better on BVI, we've now got to make sure Anguilla gets the help it needs".
However, the hospitals there "are not functioning", she said.
"We said, 'We need to do something about this".
Authorities in the devastated island nation of Antigua and Barbuda faced a historic effort ahead to rebuild. Mapp would not discuss how they would be evacuated or where to for security reasons.
The damage caused by Irma's westward spin through the Caribbean is expected to be devastating to the fragile economies of the region, which are mostly dependent on tourism, financial services, fishing or agriculture.