Overview

• UKHSA and Travel Health Pro say most cases have direct or indirect links to countries where clade Ib is circulating.
• The NHS advises calling 111 if symptoms develop after recent travel to central or east Africa with close contact to someone with symptoms.
• The clade Ib lineage is thought to be more transmissible than the clade II strain that drove the UK’s 2022 outbreak.
• WHO notes higher risk of severe outcomes for young children, pregnant people, and those with weakened immune systems, especially with poorly managed HIV.
• High vaccine coverage has kept clade IIb transmission lower since 2023, while imported clade Ib cases have also been reported in Belgium, Canada, France, Germany, Sweden and the United States.