LONDON — Britain moved decisively on Wednesday to cushion its economy from the ravages of the coronavirus, even as its more cautious medical response came under fire, particularly after a health minister who had mingled at a reception with Prime Minister Boris Johnson fell ill from the contagion.
The minister, Nadine Dorries, mixed with multiple other members of Parliament after contracting the virus, prompting at least one other lawmaker to isolate herself and raising questions about whether Mr. Johnson should do likewise and even whether Parliament should suspend its proceedings.
Parliament did meet, however, to hear Mr. Johnson’s emergency plan to head off an economic crash from what the World Health Organization on Wednesday officially described as a pandemic: 30 billion pounds, or $38 billion, in one-time spending in the budget for the overburdened National Health Service and a variety of extra benefits for firms and people forced out of work because of the virus.
As the total number of confirmed cases in Britain rose to nearly 500, the country’s aggressive economic rescue plan contrasted starkly with its public-health response to the epidemic.
The government has so far held off radical measures, like closing schools or banning large gatherings, which the authorities in Italy, France, Germany and other countries have adopted. And it has carefully regulated its flow of information to the public about what might come next.
Chancellor Angela Merkel of Germany, by contrast, warned on Wednesday that the virus would ultimately infect about two-thirds of that country’s population. “This is an exceptional situation, and we will do whatever is needed,” she said. And President Emmanuel Macron of France said, “What we are living is a true world crisis.”
British officials have avoided such language and have continued to be low key about the personal risks. Mr. Johnson does not plan to be tested, a spokesman said, because he has no symptoms and was never closer than two meters, or six feet, from Ms. Dorries, the critical distance to avoid contracting the virus.
Now, however, some experts are calling on the government to shift course — from trying to contain the virus to slowing its spread — and to be more transparent in discussing future steps. With 456 confirmed cases, and eight deaths, Britain has kept a tighter lid on outbreaks than its European neighbors. But officials warned that those numbers are likely to multiply in the coming days.
“It’s better to be ahead of the curve,” said Devi Sridhar, director of the global health governance program at Edinburgh University. “We should be banning public gatherings. I don’t know why we haven’t taken that step.”
But there was palpable alarm in Westminster, after the health minister revealed on Tuesday evening that she had tested positive for the virus. Police tape and signs saying, “COVID-19 DO NOT ENTER” went up around parliamentary offices. A member of Ms. Dorries’s staff tested positive on Wednesday, and a Labour Party lawmaker, Rachael Maskell, said the health service had advised her to self-isolate because she met with Ms. Dorries last week.
Ms. Maskell, who lives in London with her sister, told a BBC radio program that she had gone so far as to put up “a barrier at home to make sure our company doesn’t mix over the two-week period.”
The night before the Treasury presented its budget, its Westminster headquarters had to be deep-cleaned, British news outlets reported, after the partner of an official there tested positive for the coronavirus.
In presenting the budget, the chancellor of the Exchequer, Rishi Sunak, said the virus would have “a significant impact” on the economy, which is already projected to grow at its slowest rate since 2009. Warning of “tough” times ahead, he said the blow would be particularly hard for small businesses and part-time workers.
“We are doing everything we can to keep this country and our people healthy and financially secure,” said Mr. Sunak, a 39-year-old former investment banker who became chancellor only a month ago, after Mr. Johnson forced out his predecessor, Sajid Javid. “I will do whatever it takes to get our nation through it.”
The budget was once meant to showcase the post-Brexit priorities of Mr. Johnson’s new government. In a stark reversal of 40 years of Thatcher-inspired small government and fiscal restraint favored by previous Conservative governments, it includes major public-works projects to lift the fortunes of Britain’s Midlands and North, which have lagged London and the country’s Southeast as Britain’s manufacturing sector has sagged in recent decades.
Voters in those regions abandoned the opposition Labour Party in the elections in December and helped give Mr. Johnson’s Conservative Party a commanding majority in Parliament. In return, Mr. Johnson has promised to triple the average net investment over the past 40 years, raising it to its highest levels in real terms since 1955.
But history was overtaken by a health crisis, as the budget became an exercise in fiscal intensive care. Hours before Mr. Sunak presented the numbers, the Bank of England announced an emergency cut in interest rates, back down to their lowest levels in history, and pledged to free up billions of pounds of extra lending to help banks support firms through the crisis.
Taken together, Mr. Sunak said, Britain’s program of monetary and fiscal measures “represents one of the most comprehensive economic responses of any government anywhere in the world to date.”
Medical experts have generally praised Britain’s initial handling of the outbreak, when it isolated British passengers from the Diamond Princess cruise ship, where more than 700 were infected with the coronavirus and eight died. But the health service has been under heavy pressure to ramp up its bed capacity and staffing levels, both of which have been depleted by a decade of cuts to spending growth under the Conservative Party’s austerity program.
In their latest move to shore up their response, health officials said they were planning to draft nursing students to help hospital wards cope during the peak of the outbreak, which health officials say is at least a couple of weeks away.
Stuart Neil, a professor of virology at King’s College London, said the government was having to walk “a very difficult tightrope” in trying to limit the spread of the virus without exhausting the public with heavy-handed restrictions too early.
Closing soccer matches to fans, for example, would most likely only drive them to watch at pubs instead, where the virus could spread more easily than at open-air arenas, Professor Neil said.
Shutting schools presents its own host of issues: Frontline health workers would suddenly have to worry about looking after their children, and people who insist on working anyway could end up leaving their children with grandparents, exposing vulnerable people to more contacts at the very moment they should be protected.
“A lot of these measures tend to sound great on paper, but they don’t necessarily achieve what you expect them to achieve in practice,” Professor Neil said. “If you try to aggressively do some sort of massive lockdown like Italy, or some of the earlier stuff the Italians did, that can be counterproductive if people get bored and don’t adhere to it over time.”
The number of cases was slow to explode in Britain in part because the country’s health system is especially proficient at tracking down patients’ contacts and isolating them, a byproduct of a centralized health system that gives public health officials easy access to hospitals and doctors across the country, Professor Neil said.
But, he said, “Whether that has made any difference to how this epidemic subsequently evolves in this country, it’s too early to tell.”
Dr. Chris Smith, who specializes in virology at the University of Cambridge and is a host of “The Naked Scientists” podcast, agreed that averting large-scale shutdowns until the spread of the disease intensified was warranted.
So far, Dr. Smith said, the number of cases was rising fairly steadily in Britain. But cracking down on large gatherings will be most useful just when the day-over-day change in cases begins to soar, and when the number of untraceable community transmissions surges relative to the number of cases coming from abroad.
“If you intervene just ahead of that, you can blunt that and smooth out the curve,” he said, spreading out the transmission of the virus over a long enough period that the health system can cope.
“The critical thing is to intervene at the right time because you achieve the maximum bang for your buck,” he said. “People are not going to tolerate being confined to barracks indefinitely. You can only do this for so long before it becomes unsustainable.”