The Omicron variant is spreading rapidly and is likely to be cause of almost all local Covid-19 infections by the end of this month, according to the Department of Medical Sciences.

From Jan 11 to 17, Omicron was found in 97% of infected arrivals from overseas sampled for thorough checks, and 80% of local cases, with the Delta variant accounting for the rest, department director Supakit Sirilak said on Friday.

"By the end of this month, 97 to 98% of local cases will be of Omicron, and Delta will eventually disappear," Dr Supakiat said.

He added, "We will have to live with Omicron. If it is not so severe, it will finally be easier to handle. Please get the third shot of vaccine."

Thailand had logged 10,721 Omicron cases since Nov 1.

From Jan 11 to 17, Omicron infections formed 86.8% of all Covid-19 cases sampled and 80.4% of local cases, with Delta forming most of the rest.

Among the fatalities and severely ill patients, Omicron accounted for 67.2% and Delta 32.8%.

"Of the severe and fatal cases, Omicron coverage was less than its average percentage in all cases, but Delta almost doubled its 15% average. This confirms that Omicron is quite clearly less severe than Delta," Dr Supakit said.