Health minister and Conservative MP Nadine Dorries has been diagnosed with coronavirus.
Ms Dorries said she has been self-isolating at home. Labour MP Rachael Maskell said she has since been told to do the same as she had met Ms Dorries.
The Department of Health said Ms Dorries first showed symptoms on Thursday – the same day she attended an event hosted by the prime minister.
Six people with the virus have died in the UK, which has a total of 382 cases.
The latest person to die was a man in his early 80s who had underlying health conditions.
Meanwhile, a 53-year-old British woman has become the first person with Covid-19, the disease caused by the virus, to die in Indonesia, according to local media reports.
It is not clear whether the woman – who was reportedly critically ill with multiple health conditions – died due to the virus.
The Foreign and Commonwealth Office said it is “supporting the family of a British woman who has died in Indonesia and are in contact with local authorities”.
Ms Dorries, the MP for Mid Bedfordshire, said Public Health England had started tracing people she had been in contact with, and the department and her parliamentary office were closely following its advice.
The 62-year-old, who began her career as a nurse, later tweeted it had been “pretty rubbish but I hope I’m over the worst of it now”.
But she added she was worried about her 84-year-old mother who was staying with her and began to cough on Tuesday.
It is not known how many meetings Ms Dorries had attended at Westminster or in her constituency in recent days.
She was at an event at Downing Street last Thursday to mark International Women’s Day.
