MILAN, Jan 3 (Reuters) - A survey of wastewater showed the Omicron coronavirus variant spreading to a majority of regions of Italy in December, the government"s National Health Institute said on Monday. The research found the highly contagious variant in the sewage systems of 14 of the country"s 20 regions between Dec. 19 and Dec. 25, the ISS said, compared to just one region earlier in the month. Omicron was found in 28.4% of 282 wastewater samples. "Environmental monitoring of SARS-CoV-2 in wastewater is proving to be a key tool, in addition to epidemiological surveillance, for understanding the evolution of the pandemic," said study coordinator Giuseppina La Rosa. The European Union has promoted the usefulness of wastewater monitoring in detection of coronavirus mutations. read more Italy also conducts swab-based surveys to detect Omicron, with the most recent one on Dec. 23 pointing to a rapid spread. read more Italy, the first Western country to be hit by the pandemic early last year, has seen new infections rise steeply in recent weeks. Overall, it has registered 137,786 deaths linked to the virus and has reported 6.4 million cases. The country reported 68,052 new cases on Monday, against 61,046 the day before, while the daily tally of coronavirus-related deaths rose to 140 from 133. read more