Officials are trying to trace everyone she met after going to a reception with the PM the day before she felt ill
Health minister Nadine Dorries has tested positive for coronavirus and is self-isolating.
She is the first MP in the UK to be diagnosed with COVID-19, as the virus spread further on Tuesday.
A sixth person in the UK has died and the total number of confirmed cases is 382 – up by 54 in the last day.
Coronavirus: The infection numbers in realtime
In a statement, the minister in charge of patient safety said: “I can confirm I have tested positive for coronavirus.
“As soon as I was informed I took all the advised precautions and have been self-isolating at home.
“I would like to thank PHE and the wonderful NHS staff who have provided me with advice and support.”