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Professor Chris Whitty, England’s chief medical officer, is self-isolating after experiencing coronavirus symptoms.

The UK has seen its biggest day-on-day rise in deaths since the Covid-19 outbreak began, as Boris Johnson and Matt Hancock said they have tested positive for the virus.

A total of 759 people have now died in UK hospitals after being diagnosed with coronavirus, while 14,579 have tested positive, the Department of Health and Social Care said.

Hundreds of thousands more people are thought to be infected. The jump in coronavirus-related deaths in the UK from 578 to 759 is an increase of 181 – the biggest day-on-day rise and a 31% jump on the figures released on Thursday.

It comes as the prime minister and health secretary said they were self-isolating after they tested positive for coronavirus.

Johnson, who has a high temperature and persistent cough, said he would still lead the “national fightback” against the virus from his flat above No.11.

The 55-year-old noticed that he had mild symptoms on Thursday afternoon and received the test results at midnight, Downing Street said.

His pregnant partner Carrie Symonds is not with the PM, and is reportedly isolating alone in Camberwell, south London, with the couple’s dog, Dilyn.

Johnson and Hancock have been working closely with the country’s top medics, including Whitty, deputy chief medical officer Dr Jenny Harries and chief scientific adviser Patrick Vallance.

It is not known which close contacts have been tested, but Downing Street said the advice on social distancing had been observed in No.10.