Israel announces fourth jab for over-60s; hospital bosses in England brace for ‘dangerous situation’

Portugal tells people to work from home from 26 December; Sweden announces working from home and tighter social distancing rules

• Germany poised to limit social contact as Omicron sweeps Europe
• Omicron is now dominant Covid-19 variant in US, officials say
• WHO warns festive gatherings will lead to increased cases, more deaths'
• UK coronavirus updates - live

Singapore has detected a cluster of three Covid-19 cases linked to a gym, its ministry of health said late on Monday.

The variant was found in two men, aged 24 and 21, and an 18-year-old woman.

On Monday morning, a mid-level staff member, who does not regularly have contact with the President, received a positive result for a Covid-19 test.

Three days earlier, on Friday, that staff member had spent approximately 30 minutes in proximity to the President on Air Force One, on the way from Orangeburg, South Carolina to Philadelphia, Pennsylvania.