When Boris Johnson announced on March 27 that he’d tested positive for Covid-19, Brits were in shock, much as Americans were on Friday morning when they heard President Donald Trump was infected. The UK prime minister was the first leader of a major country to be hospitalized with the virus, an event that was characterized as “routine” at first before the illness took a more serious turn. Nobody knows how this will play out for Trump, just as they didn’t for Johnson. But the president’s “precautionary” hospitalization is an obvious concern given his age and weight. Thankfully, Johnson was able to return to work eventually after a stay in intensive care — a period when it wasn’t always obvious who was running Britain. At least in the US it’s constitutionally clear who takes charge should the leader become incapacitated. The bigger uncertainty is how Trump’s experience, like Johnson’s, will shape his nation’s Covid-19 policy and broader politics. Presidents and prime ministers can change a country’s direction, but what happens when events change them? A quick victory over the virus would no doubt be emboldening and lend itself to a narrative of virility and indomitability — something that has often characterized the Trump approach to Covid. A drawn-out physical struggle with lingering aftereffects, of the kind endured by Johnson, might lead to a different mix of public health and economic policies. It could also alter Trump’s performance in office, assuming he returns, and public perception of the commander in chief. It would be wrong to say it was only Johnson’s illness that forced him to take the coronavirus seriously. He’d already abandoned a Swedish-style laissez faire approach to the pandemic after an Imperial College model (later found to be flawed) suggested the British death toll could be more than half a million people. Four days before his positive test was announced, Johnson implemented a national lockdown in a sober address that marked the first major departure from his trademark boosterist style. Without draconian restrictions, he told the country, the National Health Service would be overwhelmed. Many of his fellow Conservatives thought he’d gone too far, and worried about the economic toll. Johnson’s deteriorating condition ended that argument. When it was announced that he’d been taken to an ICU, there was a nationwide intake of breath. The UK’s streets were deserted, as the public came together to obey the lockdown rules and protect the NHS. Even his political enemies wished him well. We don’t know how much viral load has entered Trump nor the strength of his body’s defenses. Like Johnson at the time, Trump is considered clinically obese, a comorbidity that increases the chances of having the virus in a more severe form. Johnson, who’d always disdained illness, put on a very British show of “carrying on” with work, a judgment that might have worsened his chances. Trump has been hospitalized immediately and treated with the experimental antibody drug cocktail by Regeneron. Like Johnson, he’ll have the best care available. Had Johnson brushed off the virus, he might have leaned more toward Sweden’s minimalist lockdown approach. Instead he returned chastened and altered. His antipathy about nanny-state interventions, such as tackling obesity, was abandoned. When urged by Tory right-wingers to reopen the economy, he was cautious. Once restrictions were eased, his messaging was often hesitant and confusing. There has been much talk about how the virus has impacted Johnson physically and mentally. We know that many of those infected, even without hospitalization, suffer lingering symptoms that can last months — ranging from fatigue to aches and an inability to focus. Johnson was never a particularly strong parliamentary performer, but his demeanor since his return has sometimes seemed more subdued, his grasp of policy poor and his speech less commanding. Last week he misrepresented his government’s own lockdown restrictions for the north of the country and had to apologize. Was that a temporary lapse from a leader under enormous pressure, and who happens to have a newborn baby at home? Or is he still struggling with Covid’s aftereffects? It almost doesn’t matter. British party politics is a blood sport. A Tory prime minister serves at the pleasure of his parliamentary party, unlike the American president. Any sign of weakness from a leader, as Theresa May’s bitter experience showed, and there are always rivals ready to pounce. Trump is not in the same situation, but he is fighting an election: A figure who depends on strongman appeal won’t be eager to show frailty, whether or not he ends up in an ICU. Cartoonish comparisons between Johnson and Trump are impossible to avoid, even beyond the distinctive blonde hairstyles. They aren’t entirely facile either. Both rode to power on a populist backlash, aided by the discontent of working class voters and the support of traditional conservatives. Even so, Trump is the far more polarizing figure and the more extreme personality. Johnson was hugely popular when the pandemic hit and had just won a handsome election victory only months before; Trump is behind Joe Biden in the polls with just over a month before the US vote. The prime minister has taken the virus seriously since March; the president downplayed it. Johnson’s gaffes, U-turns and bungling of Covid policy — and his standing by aides that break the lockdown rules — have severely diminished his public standing recently, but his attitude to the pandemic has never seemed ideological, unlike that of his US counterpart. Americans may wonder now whether a command-and-control center that couldn’t protect the president can protect them. While Britons have a long while to wait before they can express a verdict on how their government handled the pandemic, Americans will do so imminently. Bloomberg