LONDON — Prime Minister Boris Johnson of Britain once mentioned his political hero was once the mayor throughout the film “Jaws,” praising him for defying mass hysteria to stick the beaches open after a constituent is eaten via a shark.

As the coronavirus now stampedes all the way through Britain and some distance of the sector, Mr. Johnson is heeding the identical idea, spurning the mass closures that have develop into now not odd all the way through Europe and taking part in his political long run on a further restrained method.

While world places all the way through Europe have shut schools, dressed in events and even consuming puts and bars, Mr. Johnson has largely stored Britain open, opting for further targeted measures like asking other people with breathing indicators to stay area. In have an effect on, his government has mentioned that mass closures may not halt the outbreak, and that exposing a large segment of the population will help assemble immunity and limit long run infections.

That methodology has startled some epidemiologists, drawn complaint from a former neatly being secretary and political absolute best good friend, and precipitated angry requires that Mr. Johnson’s government reveal further of its reasoning.

Cases of the coronavirus in Britain, held low for weeks as officials tracked down the contacts of known victims, have now surged, rising to with reference to 800 on Friday from fewer than 600 a day quicker than. With trying out limited to clinic victims, Mr. Johnson mentioned on Thursday that the true choice of other people infected may be as many as 10,000.

President Trump, mentioning the rising case depend, mentioned Friday that he was once allowing for together with Britain to the tick list of European world places whose voters are banned from flying to the United States.

“There’s no other country in the world managing the epidemic in the same way,” Francois Balloux, an infectious sickness epidemiologist at University College London, mentioned of Britain’s method. But, he mentioned, “It’s not an insane decision. And it might actually pay off.”

The government is leaning intently on skepticism in some scientific circles regarding the effectiveness of mass closures. Some epidemiologists concern that final schools absolute best pulls front-line scientific docs and nurses transparent in their artwork, and consider that large events are a lot much less unhealthy for spreading the virus than further intimate gatherings at bars or at other people’s homes.

It has moreover mentioned that the measures it has taken, like asking other people with chronic coughs and top temperatures to stay area for a week, will reduce the spread of the virus considerably.

But British advisers are also leaning on a further contentious thought: that exposing a large proportion of the population to the coronavirus might help other people increase immunity, and put Britain in a better position to protect itself against the virus roaring once more next wintry climate.

Sir Patrick Vallance, England’s chief scientific adviser, mentioned the government was once looking “to build up some kind of herd immunity so more people are immune to this disease and we reduce the transmission.”

Herd immunity, a time frame maximum frequently used to seek advice from one of the simplest ways mass vaccinations can save you the spread of sickness and give protection to people who aren’t immune, is not noticed via many scientists as a tool to be used against the coronavirus. Mr. Vallance has mentioned that it will require more or less 60 percent of Britons to develop into infected, creating enough immunity throughout the population second surge in instances next wintry climate will also be a lot much less severe.

But professionals mentioned that was once an peculiar and untested method, and that it may well be now not imaginable to stick older and additional vulnerable other people from turning into infected too, putting them at an important chance. They cautioned that the science was once unsettled on how in short other people increase immunity to the coronavirus, and for some way long. And professionals instructed the government to show further of the evidence behind its making an allowance for.

“Herd immunity means 70 percent of people or so have been infected,” mentioned Martin Hibberd, a professor of infectious illnesses at the London School of Hygiene and Tropical Medicine. “In my mind, that’s not a desirable aim. That’s a kind of consequence of the strategy.”

Britain’s method presentations the hyper-rationalist self-image of a chief minister who has now not all the time hewed so carefully to scientists up to now, as when he now and again trafficked in discredited theories about native climate exchange.

In this situation, Mr. Johnson has formed himself for the reason that dispassionate solution to leaders all the way through Europe who have acted further aggressively.

But his government is not immune from public alarm, signaling late Friday evening time that it will reverse trail on a minimum of some sides of its method. It instructed British knowledge retail outlets that it will ban some mass gatherings, like dressed in fits and live performance occasions, starting next weekend, and lay the groundwork for added usual operating at area.

So a ways, throughout the absence of government-mandated shutdowns, private entities in Britain have taken up the slack.

Unilever, the British-Dutch consumer pieces company, mentioned on Friday that it was once ordering all its office-based employees to work from home starting next week. And the Premier League, England’s highest-level soccer league, suspended video video games until a minimum of next month.

Mr. Johnson’s government itself moved on Friday to prolong a whole lot of local elections and the London mayoral election for a 12 months after a watchdog mentioned the coronavirus would have an effect on campaigning and voting.

But Mr. Johnson has resisted other measures, like final schools, proscribing mass gatherings, steerage other people transparent of consuming puts or bars and banning crowds from dressed in events.

“They’re trying to walk this terrible balance between not alarming the public, not hurting the economy, but making sure you try to flatten this epidemic,” mentioned Roy Anderson, a professor of infectious sickness epidemiology at Imperial College London. “Is it going to work? I’m not sure, to be honest.”

The methodology amounts to a blunt admission during the British government that fighting the coronavirus proper right here was once not imaginable, and replicating the nice fortune of places like Hong Kong that have impressed further over the top social distancing a futile hope. Instead, Britain is effectively banking that its further modest restrictions will keep the outbreak limited until summer time, scientists mentioned.

By then, it hopes that the warmer local weather will reduce further transmission — even though virologists however do not know if that may cling true — and the National Health Service, free of the usual wintertime crowds, can be upper able to handle whomever is infected.

“The idea is more to minimize the number of casualties over the long term,” Professor Balloux mentioned, “and that’s completely unique. All other countries are firefighting in the short term.”

But the clamor for temporary firefighting has picked up in recent days.

Jeremy Hunt, the former neatly being secretary, who like Mr. Johnson is a Conservative lawmaker, broke ranks and referred to as for added stringent restrictions: banning visitors from nursing homes, encouraging other people to work from home and closing schools.

“I think it is surprising and concerning that we’re not doing any of it at all when we have just four weeks before we get to the stage that Italy is at,” Mr. Hunt mentioned in a television interview. “You would have thought that every single thing we do in that four weeks would be designed to slow the spread of people catching the virus.”

Some epidemiologists have moreover bristled at the government’s reliance on a private corporate of behavioral scientists, known as the “nudge unit.” That unit has assisted in shaping the government’s solution to delaying any shutdowns until later throughout the virus, at the idea that that people will get bored of staying at area by the time the outbreak is at its peak and separation is most sought after.

Helen Ward, a professor of public neatly being at Imperial College London, mentioned the government’s advisers should reveal further of their making an allowance for.

“We don’t know the evidence on which the government has made its decisions,” Professor Ward mentioned.

She moreover mentioned the government should imagine making stronger tips to older other people to scale back on their exposure. Mr. Johnson discouraged older Britons this week absolute best from going on cruises, even though many epidemiologists urge considerably stronger precautions.

And Professor Hibberd, of the London School of Hygiene, mentioned the government’s method may not rely enough on trying out. Without working out whether or not or now not Britain is suffering a further concentrated outbreak, as throughout the north of Italy, or whether or not or now not its dying price is as low as it believes, it is tricky to craft the correct response.

“If there’s something I feel is missing,” he mentioned, “it’s that they haven’t tested sufficiently.”