As with all presidents of the modern era, President Trump's Air Force One flights are funded entirely by taxpayers when they are for official government business but are partially reimbursed by his campaign when they are for political travel. So who decides which trips are political and which are official, or which portion of a mixed-purpose trip the campaign has to cover, and at what cost? It's complicated, USA Today reports. And it's mostly secret.

"It's up to the White House to determine if the trip has a political purpose," Brendan Doherty, an expert on presidential travel and fundraising at the U.S. Naval Academy, tells USA Today. "We usually don't get a full picture of what that cost is." Judicial Watch's Tom Fitton called the reimbursement formula "a magic number."

The White House's formula, created during Ronald Reagan's presidency, isn't public, nor is the cost of flying Air Force One — recent Pentagon estimates puts the cost at $165,000 to $275,000 an hour. And even when a president's trip is purely political, the Federal Election Commission requires the campaign to reimburse the government for only the estimated cost of a charter flight.

The mystery of how much taxpayers are subsidizing the political activity of sitting presidents has long frustrated open-government groups and political rivals — Trump criticized former President Barack Obama over his use of Air Force One during campaigns. But it's even murkier for a line-blurring, rally-loving president like Trump.

"The White House's calculation of travel expenses can be especially challenging when the president travels to what is intended as an official event, but then engages in impromptu partisan activity," Sen. Ron Wyden (D-Ore.) wrote White House Counsel Emmet Flood last October. "It is essential that taxpayer dollars are not used to subsidize partisan political activities." Wyden never got a reply, USA Today reports. Read more about the costs of Air Force One, and how Trump compares with Obama, at USA Today. Peter Weber

Irish Prime Minister Leo Varadkar is going back to his roots, with his office announcing on Sunday that once a week, he will work as a doctor in order to help patients during the coronavirus pandemic.

Varadkar spent seven years as a doctor, leaving the profession in 2013 when he became a politician. His office said he re-registered as a physician in March, and The Irish Times reports he will be assessing people over the phone, talking to them about their symptoms before they go to the hospital.

"Many of his family and friends are working in the health service," Varadkar's spokesman said. "He wanted to help out even in a small way." His father was a general practitioner, his mother was a nurse, and his partner is a cardiologist.

Ireland's health minister has asked former health care professionals to re-register and help staff up Ireland's Health Service Executive, and 70,000 people have responded, Reuters reports. Catherine Garcia

They've made full recoveries, and now it's time for koalas rescued during last year's devastating Australian bushfires to go back into the wild.

Science for Wildlife, a conservation organization in Sydney, released the first 12 koalas back into the Blue Mountains on March 25 and 27. Those koalas were saved in December and spent the last few months recovering at Sydney's Taronga Zoo. Dr. Kellie Leigh, Science for Wildlife's executive director, said in a statement that her team made sure conditions had improved enough to sustain the koalas.

"The recent rains have helped and there is now plenty of new growth for them to eat, so the time is right," Leigh said. "We will be radio-tracking them and keeping a close eye on them to make sure that they settle in okay."

On April 2, Port Macquarie Koala Hospital released a koala it rescued in October, and has plans to set 25 more koalas free in the next few days, The Independent reports. Sue Ashton, the hospital's president, said not only will the koalas go back to their home habitats, but in some cases, they will be returned "to their original tree." Catherine Garcia

U.S. officials and intelligence agencies started warning the White House in mid-January that the coronavirus outbreak in China could spread through the U.S. and around the world, but "the Trump administration squandered nearly two months that could have been used to bolster the federal stockpile of critically needed medical supplies and equipment," The Associated Press reported Sunday night. "A review of federal purchasing contracts by The Associated Press shows federal agencies largely waited until mid-March to begin placing bulk orders of N95 respirator masks, mechanical ventilators, and other equipment needed by front-line health care workers."

By mid-March, U.S. hospitals in hard-hit areas were treating a rising number of COVID-19 patients without adequate equipment, states were bidding against each other for masks and ventilators on the open market, and Trump was telling states the role of the U.S. stockpile was supplier of last resort. "The notion of the federal stockpile was it's supposed to be our stockpile," Jared Kushner, Trump's son-in-law and senior adviser in charge of coronavirus supply chains, said Thursday. "It's not supposed to be state stockpiles that they then use."

An AP reporter asked Trump about the federal supply shortfall at Sunday night's briefing, Trump dismissed the question and ended the briefing.

The federal emergency stockpile was created in 1999 to prepare for the Y2K issue, then was expanded after the Sept. 11, 2001, attacks and stocked up with pandemic response supplies in 2006. Greg Burel, director of the federal stockpile from 2007 until his retirement in January, told AP that based on budget allocations, it was intended only as a "bridge stock."

"States do not have the purchasing power of the federal government," said former Health and Human Services Secretary Kathleen Sebelius, who also served as governor of Kansas. "They do not have the ability to run a deficit like the federal government. They do not have the logistical power of the federal government." Now, she added, "we basically wasted two months." Read more at The Associated Press. Peter Weber

Public health experts and government officials agree that the U.S. government's coronavirus death toll almost certainly understates how many Americans have actually died from the virus.

The Centers for Disease Control and Prevention only counts deaths where the presence of the coronavirus is confirmed in a lab test, The Washington Post reports, and "we know that it is an underestimation," CDC spokeswoman Kristen Nordlund said.

There are many reasons why the numbers are underreported. Strict criteria in the beginning of the outbreak kept many people from getting tested for coronavirus, and it's still difficult to get tested in some areas, for example. There's also the matter of false positives, and not all medical examiners have tests or believe they should conduct postmortem testing, even on people who died at home or in nursing homes where there were outbreaks. Experts also believe some February and early March deaths that were attributed to influenza or pneumonia were likely due to coronavirus.

The official death count is based on reports sent by states, and as of Sunday night, the CDC reports 304,826 confirmed U.S. cases and 7,616 deaths. The Post, other media outlets, and university researchers update their numbers more frequently, with the Post reporting on Sunday night that 9,633 people have died from coronavirus in the U.S., and at least 337,000 cases have been confirmed. Catherine Garcia

A fight broke out in the White House Situation Room on Saturday, after President Trump's economic adviser Peter Navarro clashed with Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, over an unproven COVID-19 coronavirus treatment, Axios reports.

Four people with knowledge of the matter told Axios' Jonathan Swan the argument took place near the end of a White House coronavirus task force meeting, after Food and Drug Administration Commissioner Stephen Hahn brought up hydroxychloroquine, an antimalarial drug Trump has touted as a possible "game-changer" in the fight against coronavirus. When Hahn was finished giving updates on drug trials, Navarro put folders down on the table where Hahn, Fauci, Vice President Mike Pence, and others were sitting.

One person familiar with the conversation told Swan the "first words out of his mouth are that the studies that he's seen, I believe they're mostly overseas, show 'clear therapeutic efficacy.' Those are the exact words out of his mouth." Fauci responded that this was anecdotal evidence, and this "just set Peter off," Swan reports. Navarro pointed to the folders and said, "That's science, not anecdote," a source said, and as his voice continued to get louder, Pence tried to intervene. "It was pretty clear that everyone was just trying to get Peter to sit down and stop being so confrontational," another person told Swan.

Fauci and other public health officials have said more data is needed before anyone can say the drug is effective against COVID-19, but based on things he's read, Navarro is convinced it works, Swan reports. The task force ultimately decided that publicly, the White House needs to say that use of hydroxychloroquine is between doctors and patients. Read more at Axios. Catherine Garcia

Queen Elizabeth II delivered a rare televised address on Sunday, calling on the British people to keep doing their part to stop the spread of the COVID-19 coronavirus, reminding them that "while we may have more still to endure, better days will return."

On Sunday, the death toll from COVID-19 hit 4,934 in Britain. The queen declared that "together we are tackling this disease, and I want to reassure you that if we remain united and resolute, then we will overcome it. While we have faced challenges before, this one is different. This time we join with all nations across the globe in a common endeavor, using the great advances of science and our instinctive compassion to heal. We will succeed, and that success will belong to every one of us."

Queen Elizabeth thanked health care workers for their tireless efforts to save lives, as well as everyone staying at home, and said she was reminded of the 1940 address she made with her late sister Margaret. They spoke to children who were evacuated during the German bombing raids in World War II, and "today, once again, many will feel a painful sense of separation from their loved ones," she said. "But now, as then, we know, deep down, that it is the right thing to do."

The 93-year-old queen and her 98-year-old husband, Prince Philip, are at Windsor Castle. Their 71-year-old son Prince Charles tested positive for the COVID-19 coronavirus and has recovered. The queen's address was recorded in a large room, where the only other person was the cameraman, Reuters reports; he wore gloves and a mask. The queen delivers a Christmas message every year, but otherwise has only made a handful of televised addresses during her 68-year reign. Catherine Garcia