Nvidia NVDA.O was also falling. By Devik Jain, Shreyashi Sanyal and Sinéad Carew Dec 6 (Reuters) - Wall Street's major averages closed higher on Monday with economically sensitive sectors and travel-related stocks soaring as investors were encouraged by some optimistic comments from a top U.S. official on the latest COVID-19 variant. Wall Street's major indexes have been swinging wildly since Nov. 26 as investors digested news of the COVID-19 Omicron variant and then Federal Reserve Chair Jerome Powell's hawkish comments last week about a speedier tapering of government bond-buying to tackle surging inflation.