Boris Johnson Tests Positive as Global Virus Cases Surpass 500,000

Governments stepped up enforcement of measures to quell the spread of the novel coronavirus as British Prime Minister Boris Johnson tested positive for the virus and the number of people infected world-wide climbed above half a million.

Mr. Johnson, 55, went into isolation after experiencing mild symptoms of illness, his office said Friday. Mr. Johnson will continue to lead Britain’s response to the pandemic, the government said.

World-wide there were more than 537,000 confirmed cases of coronavirus infection and 24,354 deaths from Covid-19, the pneumonialike illness caused by the virus,...