The World Health Organization (WHO) said Tuesday it is not clear yet whether the Omicron coronavirus variant is more transmissible or causes more or less severe illness.

“It is yet to be seen how and whether the latest Covid-19 variant of concern Omicron will be more transmissible or more or less severe,“ WHO’s Regional Director for Europe Dr. Hans Kluge said at a news conference.

There have been some positive signs coming from South Africa, where the Omicron variant accounts for the majority of new coronavirus infections. Doctors there have reported that cases caused by the variant are generally mild, although they cautioned these are early days.

During the briefing, which focused on Europe and Central Asia, Kluge said that while the Omicron variant is “in sight and on the rise,” it is the Delta variant that is the problem in the region right now.

“However we succeed against Delta today is a win over Omicron tomorrow before it eventually surges,” Kluge said, adding: “We are in the business of stabilizing a pandemic and that means not one variant at a time, but all variants at once.”