As the coronavirus outbreak sweeps across the world, governments, companies and investors are grappling with the biggest public health crisis since the 1918 influenza pandemic, panicked populations and imploding financial markets.

After ordering the closure of schools across a country that casts itself as a pillar of Western stability, Johnson on Wednesday said the government was ruling nothing out when asked whether he would bring in measures to lock down London.

Johnson has asked the government to come up with plans for a so-called lockdown which would see businesses closed, transport services reduced, gatherings limited and more stringent controls imposed on the population of one Europe's richest city.

Pressed at a news conference whether tougher measures were needed to shut down London where bars, public transport and businesses remain busy, Johnson said: "We've always said we're going to do the right measures at the right time."

London's transport authority said it would close up to 40 underground train stations until further notice and prepared to cut down other services including buses and trains, including the whole of the Waterloo & City line.

"People should not be travelling, by any means, unless they really, really have to," London Mayor Sadiq Khan said.

Buckingham Palace announced on Thursday that Queen Elizabeth had agreed to postpone the planned state visit by Japanese Emperor Naruhito in June.

Britain has so far reported 104 deaths from coronavirus and 2626 confirmed cases.

Australian Associated Press