Coronavirus-infected British Prime Minister Boris Johnson was “improving” and sitting up in bed as he began his fourth day in intensive care Thursday — but he could still be out of action for at least a month, according to reports.

“Things are getting better for him,” culture minister Oliver Dowden said. “He’s stable, improving, sat up and engaged with medical staff,” he said.

The 55-year-old leader had revealed he had tested positive for COVID-19 on March 27, almost two weeks ago.  After initially appearing upbeat — continuing to lead his government via video conferences — he was taken to London’s St Thomas’ Hospital on Sunday, needing oxygen and intensive care the following day.

Even with him appearing to be over the worst, Johnson could still be out of action for a month, The Sun claims.

The paper notes medical advice for seriously ill patients needing one week of recuperation for every day spent in an ICU — which would mean a month for the PM, more if he remains in the specialist ward longer.

“The Prime Minister will absolutely follow the advice of his medical team,” his spokesman told the paper.

Foreign Secretary Dominic Raab is currently running the government in Johnson’s absence.

With Post wires