Patel says new measures are to be introduced at the UK border to guard against a second wave of infections.
Anyone entering the UK, from 8 June, will have to self-isolate for 14 days.
The home secretary says there is a risk that people visiting the UK over the summer or returning from holidays abroad might bring the virus with them.
With the infection rate in the UK falling, imported cases could pose a “larger threat” going forward, she says, and action is needed to manage the risk of transmission this way.
As was speculated earlier, those arriving from the Republic of Ireland, the Channel Islands and the Isle of Man will be exempt.
Others excluded are the medical professionals helping to treat the virus and seasonal agricultural workers staying on the farms where they are working.