There is an “increased likelihood” of a new virus, which has killed 17 people in China, being found in the UK, the health secretary has said. 

But in a statement to the Commons, Matt Hancock insisted that the country was “well prepared” for any potential cases of coronavirus, which is believed to have originated in the city of Wuhan. 

He told MPs on Thursday: “The chief medical officer has revised the risk to the UK population from ‘very low’ to ‘low’ and has concluded that while there is an increased likelihood that cases may arise in this country, we are well prepared and well equipped to deal with them.”

UK travellers have been warned against “all but essential travel” to Wuhan, and Chinese visitors to the UK will be given advice on what to do if they fall ill during their trip.

Hancock explained: “Since yesterday, Public Health England officials have been carrying out monitoring of direct flights from Wuhan city and all passengers on direct flights from China will receive information on what to do if they fall ill.”

He added: “Acting on the advice of [chief medical officer] Professor Whitty we have updated our travel guidance to British citizens to advise against all but essential travel to Wuhan city.”

It emerged on Thursday morning that a second city in China had been placed on lockdown after the outbreak of the new virus.

Transport links in and out of Huanggang, which is home to some six million people, have been cut off and residents asked not to leave as the number of cases of coronavirus increases. 

The city is little more than an hour from Wuhan, where all transport links, including road, bus, ferry, subway, and air travel were suspended on Thursday morning. 

Those living in both cities have been asked not to leave, except under exceptional circumstances. 

Officials have reported 600 confirmed cases of the new coronavirus, as health authorities around the world scramble to prevent a global pandemic.

Health officials fear the transmission rate will accelerate as hundreds of millions of Chinese travel at home and abroad during week-long holidays for the Lunar New Year, which begins on Saturday.

Addressing the UK’s preparedness for potential cases of the virus, Hancock said on Thursday morning: “The UK is one of the first countries to have developed a world-leading test for the new coronavirus.

“The NHS is ready to respond appropriately to any cases that emerge.

“Clinicians both in primary and secondary care have already received advice covering initial detection and investigation of possible cases, infection prevention and control and clinical diagnostics.”

He added: “We are working closely with our counterparts in the devolved administrations and the public can be assured that the whole of the UK is always well-prepared for these types of outbreaks.

“And we’ll remain vigilant and keep our response under constant review in the light of emerging scientific evidence.” 

The previously unknown virus strain is believed to have emerged late last year from illegally traded wildlife at an animal market in Wuhan.

Chinese authorities gave no new details on the numbers of virus infections but it has been reported in Beijing, Shanghai and Hong Kong, and several other countries including the United States – stoking fears it is already spreading worldwide.

Wuhan’s city government said it would shut down all urban transport networks and suspend outgoing flights from 10am (2am GMT).

State media broadcast images of one of Wuhan’s transport hubs, the Hankou rail station, nearly deserted, with gates blocked or barred. The government is urging citizens not to leave the city. 

State media reported highway toll booths around Wuhan were closing down, which would effectively cut off road exits. Guards were patrolling major highways, one resident told Reuters.

As the city slipped into isolation, residents thronged into hospitals for checks and scrambled for supplies, clearing out supermarket shelves and queuing for petrol.

Authorities in Huanggang ordered indoor entertainment venues, including cinemas and internet cafes, to close and were asking citizens not to leave other than under special circumstances, state media said.

Authorities had confirmed 571 cases and 17 deaths by the end of Wednesday, China’s National Health Commission said. Earlier, it said another 393 suspected cases had been reported.

Of eight known cases worldwide, Thailand has confirmed four, while Japan, South Korea, Taiwan and the United States have reported one each.

In a report on Wednesday, Imperial College London said it estimated a total of 4,000 cases of the coronavirus in Wuhan alone as of January 18, an infection rate based on the number of cases reported in China and elsewhere.

How has China responded?

In contrast with its secrecy over the 2002-03 Severe Acute Respiratory Syndrome (SARS) that killed nearly 800 people, China’s government has provided regular updates to avoid panic ahead of the holidays.

During a visit to Wuhan, vice premier Sun Chunlan said authorities needed to be open about the virus and efforts to contain it, the official Xinhua news agency said.

The World Health Organization (WHO) has said it will decide on Thursday whether to declare the outbreak a global health emergency, which would step up the international response.

If it does so, it will be the sixth international public health emergency to be declared in the last decade.

Some experts believe the new virus is not as dangerous as previous coronaviruses such as SARS and Middle East Respiratory Syndrome (MERS), which has killed more than 700 people since 2012.

“The early evidence at this stage would suggest it’s not as severe,” Australia’s chief medical officer Brendan Murphy told reporters.

WHO Director-General Tedros Adhanom Ghebreyesus told reporters in Geneva that China’s actions were “very strong” but called on it to take “more and significant measures to limit or minimise the international spread”.

“We stressed to them that by having a strong action not only they will control the outbreak in their country but they will also minimise the chances of this outbreak spreading internationally. So they recognise that,” he said. 

How have residents reacted?

There is no vaccine for the virus, which can spread through respiratory transmission. Symptoms include fever, difficulty in breathing and a cough, similar to many other respiratory illnesses.

Preliminary research suggested the virus was passed on to humans from snakes, but government medical adviser Zhong Nanshan has also identified badgers and rats as possible sources. Confirmed sufferers include 15 medical workers.

Many Chinese were cancelling trips, buying face masks and avoiding cinemas and shopping centres, and even turning to an online plague simulation game as a way to cope.

The release of seven movies over the Lunar New Year has been postponed. The holiday is the high season for distributors and cinemas attract huge crowds.

Airports globally stepped up screening of passengers from China and the European Centre for Disease Control and Prevention said the further global spread of the virus was likely.