Seven months after he battled a serious case of Covid-19, the disease caused by the coronavirus, Prime Minister Boris Johnson of Britain announced on Sunday that he was quarantining after coming into contact with a lawmaker later found to be infected.
Mr. Johnson’s office said in a statement that he felt fine and was showing no symptoms.
Experts say it is still too early to know how long immunity to the coronavirus lasts, but reinfection with the virus is thought to be very rare for at least many months after the first illness.
Mr. Johnson went into isolation after the National Health Service’s test-and-trace program contacted him and said he had been exposed to the coronavirus. On Thursday, he spent about half an hour with a member of Parliament who tested positive after feeling ill.
Other than isolating himself, Mr. Johnson is conducting business as usual, officials said. “He will carry on working from Downing Street, including on leading the government’s response to the coronavirus pandemic,” his office’s statement said.
The prime minister had a close call with the virus in April, when he was hospitalized and spent three days in intensive care.
Mr. Johnson has been accused repeatedly of taking a lackadaisical approach to the pandemic, but when he emerged from the hospital he appeared chastened.
In an emotional five-minute video, Mr. Johnson thanked the country’s National Health Service, declaring it had “saved my life, no question.”
Over three months in the summer, the portion of people in Britain with detectable antibodies to the coronavirus fell by about 27 percent. Experts say it’s normal for levels of antibodies to drop after the body clears an infection. However, when needed, immune cells already carry a memory of the virus and can churn out fresh antibodies.
In other developments around the world:
Officials in the impoverished Gaza Strip announced more than 400 new infections on Sunday, the highest single-day total since the first cases of community transmission were discovered in the territory in late August. The authorities ordered almost all shops to start closing down at 5 p.m. A nightly curfew beginning at 8 p.m. is already in place. As of Sunday morning, 10,532 people in Gaza — whose population is relatively young — have been infected and 48 have died, according to the Health Ministry.
India will fly doctors into the region around New Delhi, double the number of tests it carries out and ensure that people wear masks, in an effort to contain the spread of coronavirus in the capital, officials said on Sunday, according to Reuters. “Delhi has witnessed a huge surge in daily active cases which is likely to worsen over next few weeks,” the health minister, Harsh Vardhan, said in a tweet.