Both patients at the Manchester Royal Infirmary in northern England have been isolated for treatment, the local public health trust said in a statement.
"Manchester Royal Infirmary accident and emergency department will be closed until further notice while further investigations take place," it said.
The last person to be diagnosed with the potentially deadly virus in Britain was in February 2013, although there has been a recent increase in cases in the Middle East and a deadly outbreak in South Korea.
There is no known vaccine for MERS, a viral respiratory disease which has killed 490 people -- almost all of them in Saudi Arabia -- since it was first reported in 2012, according to the World Health Organisation.
