Tests for coronavirus are being increased to include people displaying flu-like symptoms at 11 hospitals and 100 GP surgeries across the UK.
The tests will provide an “early warning” if the virus is spreading, Public Health England medical director Prof Paul Cosford said.
It comes as more schools closed or sent staff and pupils home following trips to Italy, which has over 300 cases.
Prof Cosford told BBC Radio 4’s Today programme: “We are heightening our vigilance because of the apparent spread of the virus in countries outside mainland China.”
Up to now, people were tested only if they displayed symptoms having recently returned from one of the countries where there has been an outbreak, including China, South Korea and northern Italy.
However, Prof Cosford said Public Health England was now working with hospitals and GP surgeries to conduct “random” tests.
These will target some patients with coughs, fevers or shortness of breath, regardless of whether they have travelled to a place where the virus is spreading.
“If we do get to the position of a more widespread infection across the country, then it will give us early warning that’s happening,” said Prof Cosford.
He said the UK was still in the “containment” phase of dealing with the coronavirus, and added that efforts to identify and isolate people with the virus returning to the UK were “working really quite well”.
Prof Cosford said Public Health England was not giving “blanket advice” that schools should close if staff or pupils have travelled to areas with outbreaks of the virus.
But, he said, schools made “difficult decisions” according to their specific circumstances.
Another school, St Christopher’s C of E High School in Accrington, told parents it would be closed on Wednesday as a precautionary measure after some pupils returning from Pila in the Italian Alps said they felt unwell.