American President Trump revealed early Friday morning that he and the first lady, Melania Trump, had tested positive for the coronavirus, throwing the nation’s leadership into uncertainty and worsening the crisis caused by a pandemic that has already killed more than 207,000 Americans and harmed the economy.

Mr. Trump, who for months has played down the seriousness of the virus and hours earlier on Thursday night told an audience that “the end of the pandemic is in sight,” will quarantine（隔离） in the White House for an unspecified period of time.

For months, Mr. Trump has refused to wear a mask in public on all but a few occasions and has repeatedly questioned their effectiveness. And as recently as Tuesday, at their opening debate, he laughed at Mr. Biden for wearing one. It was not immediately clear whether Mr. Trump had already been infected by the virus at the time of the debate with Mr. Biden, 77, although the two stood far across stage and never got within six feet of each other.

The symbolism of an infected American president could frighten governors, as well as business owners trying to assess when and how to reopen or keep open shops, schools, parks, beaches, restaurants, factories and other workplaces. Eager to restore social order before the election, Mr. Trump has dismissed health concerns to demand that schools reopen, college football resume play and businesses return to full operation.

Under the 25th Amendmen（t     宪法修正案）, a medically incapable president has the option of temporarily transferring power to the vice president and can regain his authority whenever he considers himself fit for duty.

In American history, since the amendment was passed in 1967, presidents have done so only three times. In 1985, President Ronald Reagan had a surgery and briefly turned over power to Vice President George Bush. President George W. Bush did invoke（援引）the amendment twice in temporarily turning over power to Vice President Dick Cheney during medical checks in 2002 and 2007.

Tobacco ruins lives, leading to over 400,000 hospital admissions a year, and ultimately kills two in three lifetime smokers.

Over the coming weeks, MPs (议员) will debate new laws to create a “smoke-free generation”, meaning no one born on or after 1 January, 2009, can be legally sold a cigarette. This is a truly transformative piece of public health policy that could see an end to tobacco use in England.

The policy will see the legal age for being sold tobacco rise by one year each year from 2027. While the proposed age increase approach is novel, we know that raising the age of purchasing works. Smoking rates dropped by 30 per cent among young people within a year when the legal age increased from 16 to 18 in 2007. The drop was closer to 40 per cent among the target age group when it was raised from 18 to 21 in the US.

There are concerns among some that the new policy could drive an illegal market, but the evidence doesn’t back this up.

Since 2000 the illegal market for tobacco has declined from 22 per cent to 11 per cent despite raising the age of purchasing to 18, banning smoking in public places, introducing plain packaging, and continued price rises. Furthermore, the focus of the policy is to prevent people taking up smoking — no one who can currently buy tobacco will be unable to do so — making it unlikely there will be an increased demand for illegal tobacco.

Online sales may also present their own difficulty as the new policy comes into force, with digital retailers (零售商) having responsibility to check on the age of customers remotely. The government is promising “enhancing online age verification (验证)” but it would be far simpler to ban online tobacco sales altogether, as recommended in a recent independent government review.