LONDON (Reuters) - British Prime Minister Boris Johnson is self-isolating after coming into contact with someone who tested positive for COVID-19, a fresh setback after infighting among his top advisers plunged Downing Street into chaos last week.Johnson, who was admitted to intensive care in a London hospital earlier this year with the novel coronavirus, is well and does not have any symptoms, a spokesman for the prime minister said on Sunday. “He will carry on working from Downing Street, including on leading the government’s response to the coronavirus pandemic,” the spokesman said. “The prime minister will follow the rules and is self-isolating.” Johnson met lawmakers in Downing Street on Thursday, including Lee Anderson, a Conservative Party member who subsequently developed COVID-19 symptoms and tested positive.