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 country has died and the total number of confirmed cases is 382 – up by 54 in the last day.
Ms Dorries, the minister in charge of patient safety, said in a statement: “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.
“Public Health England (PHE) has started detailed contact tracing and the department and my parliamentary office are closely following their advice.
“I would like to thank PHE and the wonderful NHS staff who have provided me with advice and support.”
She added in a tweet: “It’s been pretty rubbish but I hope I’m over the worst of it now. More worried about my 84yo mum who is staying with me and began with the cough today. She is being tested tomorrow.”
Health Secretary Matt Hancock said he was “really sorry” to hear the news but that “she has done the right thing by self-isolating at home”.
He added: “We all wish her well as she recovers.
“I understand why people are worried about this disease. We will do all we can to keep people safe, based on the best possible science.”
Ms Dorries’ diagnosis was confirmed on Tuesday.
A Department of Health and Social Care (DHSC) spokeswoman said she first exhibited symptoms at some time on Thursday – the same day she attended a Downing Street event hosted by Boris Johnson to mark International Women’s Day.
Number 10 did not comment on whether the prime minister had undergone testing for the coronavirus, or whether he will now be tested.
A DHSC spokeswoman said Ms Dorries, 62, has been self-isolating at home since Friday.
Officials have begun the process of getting in touch with everyone Ms Dorries has come into contact with since displaying symptoms.
The DHSC spokeswoman initially said all health ministers including health secretary Matt Hancock were to undergo testing for the virus, but later retracted the statement.
A Government source said officials and MPs should continue to go to work in Whitehall and Parliament unless told otherwise.
“CMO (Chief Medical Officer) advice is that no one needs to self-isolate or be tested unless asked to by the PHE contact tracers who are working round the clock,” the source said.
After Ms Dorries’ diagnosis, a Parliament spokesman said there were still no plans to suspend Parliament to prevent the spread of the virus.
Hannah Bardell, an SNP MP, said that would be tough as “Westminster by its nature means we’re all corralled in there together at close proximity”.
She added: “It’s possibly one of the most germ infested unhealthy places I’ve ever worked.”
Ms Dorries has voted twice in the House of Commons in the past week, according to parliamentary records – likely meaning she has been in close contact with hundreds of other MPs.
Sky News’ political editor Beth Rigby said that “as a health minister in contact with other health ministers and officials the obvious question is whether there has been wider transmission in Department of Health team”.
“I understand Matt Hancock is in good health and not displaying any symptoms,” she added.
Politicians from across the political divide sent messages wishing Ms Dorries a swift recovery.
Labour shadow cabinet member Luke Pollard tweeted: “Politics should not get in the way of being decent human beings to one another.”