Johnson's 10 Downing St. office said Sunday that the prime minister was alerted overnight by the test-and-trace phone app. He had a meeting on Friday with Health Secretary Sajid Javid, who tested positive for COVID-19 on Saturday. Javid, who has been fully vaccinated, says he is experiencing mild symptoms.

People who are notified through the app are supposed to self-isolate, though it is not a legal requirement. Contacts of positive cases usually are advised to self-isolate for 10 days.

But Johnson's office says the prime minister will instead take a daily coronavirus test as part of an alternative system being piloted in some workplaces, including the government.

The same applies to Treasury chief Rishi Sunak, who also was contacted after meeting Javid. The government says the two men “will be conducting only essential government business during this period.”

Britain is experiencing rising coronavirus cases, and an associated “pingdemic” of hundreds of thousands of people being told to quarantine because they have been near someone who tested positive. Businesses including restaurants, car manufacturers and the London subway say they are facing staff shortages because of the self-isolation rules.

Jonathan Ashworth, health spokesman for the opposition Labour Party, said many people would be angry that there is a special “VIP” lane to avoid self-isolation.

“Waking up this morning to hear that there is a special rule, an exclusive rule, for Boris Johnson and Rishi Sunak, they will be saying that this looks like one rule for them and something else for the rest of us,” he told Sky News.

Johnson was seriously ill with the coronavirus in April 2020, spending three nights hospitalised in intensive care.

His latest exposure comes as his government prepares to lift remaining lockdown measures on Monday. Nightclubs can reopen in England for the first time since March 2020, sports and entertainment venues can admits capacity crowds and face masks are no longer mandatory indoors.

But the government is urging people to be cautious, as cases surge because of the highly transmissible delta variant of the virus first identified in India. More than 54,000 new infections were confirmed on Saturday, the highest daily total since January.

Hospitalisations and deaths are also rising, but remain far lower than at previous infection peaks thanks to vaccination. More than two-thirds of British adults have had both shots of a vaccine.

British officials are looking nervously at Israel and the Netherlands, both of which opened up society after vaccinating most of the population. Both countries have recently reimposed some restrictions after new infection surges.