The World Health Organization has warned that the global risk from the omicron variant is very high based on the early evidence and may lead to surges with “severe consequences.”

The assessment from the U.N. health agency, contained in a technical paper issued to member states, amounted to strongest, most explicit warning about the new version.

WHO said there are considerable uncertainties about the omicron variant. However, it said preliminary evidence raises the possibility that the variant has mutations that could help it both evade an immune-system response and boost its ability to spread from one person to another.