British Prime Minister Boris Johnson says he has tested positive for coronavirus, showing mild symptoms, becoming the first head of a European government to become infected by COVID-19.

He joined other leaders such as German Chancellor Angela Merkel and Canadian Prime Minister Justin Trudeau who have led their countries from self-isolation. Merkel tested negative for the virus on Monday after having contact with a doctor who later tested positive. Trudeau's wife, Sophie, tested positive earlier this month following a visit to London.

"Over the last 24 hours I have developed mild symptoms and tested positive for coronavirus," Johnson said. "I am now self-isolating, but I will continue to lead the government’s response via video-conference as we fight this virus."

A Downing Street spokesman said Johnson, 55, experienced mild symptoms on Thursday, a day after he answered at the prime minister's weekly question-and-answer session in the chamber of the House of Commons.

"The prime minister was tested for coronavirus on the personal advice of England's Chief Medical Officer, Professor Chris Whitty," the spokesman said.

"The test was carried out in No 10 by NHS staff and the result of the test was positive," the spokesman said.

When Britain clapped for health workers on Thursday evening, Johnson and his Finance Minister Rishi Sunak came out of separate entrances on Downing Street and did not come into close contact, according to a Reuters photographer at the scene.

Previously the government has said that Johnson had the option to delegate to Foreign Secretary Dominic Raab if needed.

"The prime minister was tested for coronavirus on the personal advice of England's chief medical officer, professor Chris Whitty," the spokesman said.

"The test was carried out in No. 10 by NHS staff and the result of the test was positive," the spokesman said.

U.K. Health Secretary Hancock also tested positive for COVID-19, and is now self-isolating at home, showing mild symptoms.

So far, 578 people in the United Kingdom have died after testing positive for coronavirus and the number of confirmed cases has risen to 11,658. The U.K. toll is the seventh worst in the world, after Italy, Spain, China, Iran, France and the U.S., according to a Reuters tally.

Britain's Prince Charles, the 71-year-old heir to the British throne, tested positive for coronavirus earlier this week but is in good health and is now self-isolating at his residence in Scotland with mild symptoms along with his wife Camilla, who tested negative, his office said.