The deadly coronavirus outbreak in China could reach Britain because borders are too ‘porous’ to keep the infection out, experts have said.
At a briefing in central London, virologists warned that some 4,000 people were probably now infected in the city of Wuhan, but said it could be as many as 9,700.
There have been 460 confirmed cases so far, and nine deaths, putting the fatality rate on par with the 1918 Spanish Flu epidemic, which wiped out 50 million people globally.
Experts said more deaths were expected in the coming days and the World Health Organisation (WHO) is considering declaring an international public health emergency.
The virus is also on the move, with probable cases now detected in Mexico, Hong Kong, the US, Japan, Thailand and South Korea.
On Wednesday the Department of Health announced that all direct flights from Wuhan to Britain will be met by Port Health teams to check for symptoms of coronavirus.
However on Wednesday night, passengers arriving from Wuhan to Heathrow Airport said they were not assessed.
"There was no screening at Wuhan, and there was no screening as I landed. We were given a leaflet in English saying 'if you’re experiencing any symptoms call NHS direct'.. It was quite sparse, the leaflet. I’ve not had my temperature checked," one passenger told the BBC.
But Prof Neil Ferguson, Director of the Medical Research Council’s Centre for Global Infectious Disease Analysis at Imperial College London, said it was difficult to detect the virus because it had an incubation period of five days, meaning people could be carriers yet appear symptomless.
Asked if the virus was already here Prof Ferguson said: “We can’t rule out the possibility. Border screening and the alert in the health system, is not 100 per cent foolproof.
“This sort of measure of trying to identify people who are sick coming off a plane will only identify, if you're lucky, people who will have fever coming off a plane.
“If somebody was infected two days before they travelled, they will arrive without any symptoms at all.
“It's understandable countries want to try and reduce the threat by various measures at the border. But the border will still be porous.”
There are three direct flights a week that arrive at Heathrow from Wuhan and passengers will be warned by the pilot to report symptoms, as well as being checked as they leave the plane. Leaflets and information are being handed out to travellers from China on what do to if they feel unwell.
The move comes as Public Health England (PHE) upgraded the risk to the UK population from coronavirus from "very low" to "low".
Travellers to China were warned to maintain good hand, respiratory and personal hygiene and should avoid visiting animal and bird markets or people who are ill with respiratory symptoms.
Symptoms of coronavirus can include fever, cough, shortness of breath and breathing difficulties.
Individuals were told to seek medical attention if they develop respiratory symptoms within 14 days of visiting Wuhan, either in China or on their return to the UK, but must phone ahead to avoid spreading the infection.
There are currently no confirmed cases of this new infection in the UK and the Department of Health said the NHS was on alert and well prepared to manage new diseases.
Dr Nick Phin, Deputy Director, National Infection Service, Public Health England, said: “This is a new and rapidly evolving situation where information on cases and the virus is being gathered and assessed daily.
“Based on the available evidence, the current risk to the UK is considered low. We are working with the WHO and other international partners, have issued advice to the NHS and are keeping the situation under constant review."
The new virus, which bears similarities to Sars and Mers, has never been seen before, and public health experts are trying to find out where it originated. They suspect it was passed from animals to humans and now know it can be passed between humans.
Dr Andrew Freedman, Reader in Infectious Diseases at Cardiff University, said: “It is likely that further cases will be seen in other countries around the world, including the UK and Europe, in the days & weeks to come.
“ Although person to person spread of the virus has occurred, including from patients to healthcare workers, it is not clear just how contagious it is.
“The WHO is monitoring the situation closely and may decide to declare an international public health emergency.”