Three of the patients caught the coronavirus in the UK - they are known to be contacts of someone who already had it, and were found through contact-tracing, Professor Chris Whitty said.
Another of the patients, from Essex, has not been abroad and it is not clear where they contracted the virus.
The eight others caught the virus abroad - six had recently traveled to Italy and two had been to Iran.
The new cases bring the total number of confirmed in the UK to 35, including one in Wales and one in Northern Ireland.
Earlier, UK Health Secretary Matt Hancock said that in the event of a widespread outbreak in the UK, all options to contain the virus would be on the table, including banning large events and locking down cities.
March 1, Australia and Thailand officially confirmed the first deaths from the coronavirus CoVID-2019, as Reuters reported.
In Australia, the former passenger of the Diamond Princess cruise ship, who was transported from Japan and quarantined, died. He died in a hospital in Perth. The man was 78 years old.
His widow is also infected with the virus. Her condition is stable. According to the latest government data, the number of viral infections in Australia has grown to 26.
"We monitor and respond to the information that we receive every day. We are not insured, but we are prepared as much as possible for any country, and we can handle it," Australian Prime Minister Scott Morrison wrote.
In Thailand, a 35-year-old man who also had dengue fever died of coronavirus. This was announced by Suwanchai Wattanayingcharoen, Director-General of the Department of Disease Control.
The deceased man worked in retail and often contacted tourists. Doctors and authorities suggest that he was infected with the virus.