The United Nations health emergencies chief also said on Wednesday "it's way too early" to predict the beginning of the end of China's virus outbreak.
Chief Medical Officer for England Professor Chris Witty confirmed the ninth case of coronavirus in the UK.
He said: "One further patient in England has tested positive for novel coronavirus (COVID-19), bringing the total number of cases in the UK to nine.
"This virus was passed on in China and the patient has now been transferred to a specialist NHS centre at Guy's and St Thomas' in London."
How one man spread the virus
Mr Walsh, a 53-year-old scout leader from Hove in East Sussex, contracted coronavirus on a business trip to Singapore - and is linked to five other people diagnosed with it in the UK.
On his way back to the UK from Singapore, he stopped off at a ski region in France, where five other Britons were subsequently infected with coronavirus, now also known as Covid-19.
Mr Walsh is also linked to a Briton taken ill in Majorca, taking the number of confirmed cases linked to him to 11.
The latest case comes as the two-week quarantine at Arrowe Park Hospital in Merseyside of 83 UK nationals flown back to Britain from Wuhan is set to end on Thursday morning, amid reports they have all tested negative for coronavirus.
Of the nine people so far diagnosed with coronavirus in the UK, two are GPs.
Officials know that the pair worked at a nursing home, Worthing Hospital A&E and two GP practices between them.
Public Health England (PHE) confirmed on Wednesday it has traced and advised all close contacts of the two GPs, including about 12 patients.
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Tim Loughton, Conservative MP for East Worthing and Shoreham, said on Wednesday that a number of GPs from Brighton were among those staying in the French ski chalet with Mr Walsh.
He said one of those completed a locum shift at Worthing A&E last week and, as a precaution, the hospital has now "sent home for self-isolation a number of their staff from various departments of the hospital".
As a result, the hospital is experiencing some staff shortages, he said.