Prime Minister Boris Johnson has advised Britons to cut down on their social life and work from home if possible as he ordered the elderly and infirm to isolate for 12 weeks, ramping up the battle against the coronavirus outbreak as it accelerates towards its peak.

Johnson had faced backlash as his government takes a less stringent approach to tackling the virus than countries such as Italy, France and Spain which have effectively locked down much of Europe.

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In a toughening of the United Kingdom's approach, on Monday, Johnson told reporters: "What we are announcing today is a very substantial change in the way that we want people to live their lives and I can't remember anything like it in my lifetime."

Flanked by the government's top scientist and top doctor at a new daily news briefing focused on the virus, he added: "I don't think there's really been anything like it in peacetime and we have to accept that it's a very considerable psychological, behavioural change that we're asking you, the public, the nation to do."

The number of confirmed coronavirus cases in the UK has risen to 1,543, up from 1,372 the day before, the health ministry said on Monday. The UK death toll rose to 53.

Heavily pregnant women advised to stay home

People should avoid pubs, clubs, restaurants, cinemas and theatres, the government said, although Johnson stopped short of ordering them to close.

He said he hoped venues would take a responsible approach. People should also avoid unnecessary travel and work remotely where possible, he said.

"The advice for non-essential social contact is particularly important for people over 70 years old, pregnant women and for those with some health conditions," Johnson said, confirming the government has added expectant mothers in their third trimester to the list people who should be taking extra care.

At the weekend, a newborn baby tested positive for coronavirus in north London. It was not clear whether the baby contracted the virus from the mother, or after being born.

It is not yet clear what effect the virus could have on pregnant women or newborn babies.

"At present, there is one reported case of a woman with COVID-19 who required mechanical ventilation at 30 weeks' gestation, following which she had an emergency caesarean section and made a good recovery," according to the Royal College of Obstetricians and Gynaecologists. "There are currently no data suggesting an increased risk of miscarriage or early pregnancy loss in relation to COVID-19."

The limits on social contact could last for months or at least weeks, Chief Medical Officer for England Chris Whitty said.

Johnson said anyone with symptoms of the coronavirus should isolate along with their entire household for 14 days. Homeworking, he said, should begin in earnest.

The pound sterling fell to its lowest against the US dollar since October while Johnson was speaking, down two-thirds of a cent on the day.

But Johnson downplayed the effect on the economy, saying the current market turmoil was not like the 2008 financial crisis.

"This is unlike 2008, there isn't a systemic problem within the economy," Johnson said. "If we can get the disease under control ... then there is absolutely no reason why economies worldwide should not come roaring back.

"It looks as though we are now approaching the fast growth part of the upward curve and without drastic action, cases could double every five or six days," Johnson said.

He said it was essential to ensure "those with the most serious health conditions are largely shielded from social contact for around 12 weeks."

The UK may need to close schools to slow the spread of coronavirus but now is not the time for this, the government's chief scientific adviser, Patrick Vallance, said.

"At some point, as we've said, it may be necessary to think about things like school closures. But those things, again, need to be done at the right time in the right way, at the right stage of the outbreak," Vallance said.