LISBON, Dec 17 (Reuters) - Portugal said on Friday it estimated infections with the fast-spreading coronavirus variant Omicron were doubling every two days and could account for 80% of all new cases by the end of December. The current prevalence of Omicron in Portugal was around 20%, health minister Marta Temido told a news conference. That rate would mean many more people had come down with Omicron than the latest official tally of 69 confirmed cases. "It may be of 50% in the Christmas week and 80% in the last week of the year," the minister added. The country, which has one of the world"s highest rates of vaccination against COVID-19, reported 5,800 new infections on Wednesday in the highest daily jump since early February, when it faced its toughest battle against the virus. Deaths and hospitalisations, however, remain far below levels seen during that period. "We still know too little about the variant in question. We know that it is more transmissible than Delta... the estimated time in which cases double is two days." Temido stopped short of announcing new measures, but said more needed to be done to control contagion and that the next few days will be decisive in understanding the impact of the new variant. For now at least, she said "more mask-wearing, more testing, more vaccination, more border control" is necessary. Portugal has already ordered all passengers flying into the country to show a negative test on arrival. read more Remote work will be mandatory and schools will be closed in the first week on January. Prime Minister Antonio Costa said on Thursday those restrictions cold be extended as Omicron spread.