Sterling firmed on Thursday as the discovery of the first case of the Omicron variant in the United States weighed on the dollar overnight, but trading was choppy amid uncertainty about whether the Bank of England would hike interest rates this month. Trade was volatile as daily COVID-19 infections doubled in South Africa, where Omicron has quickly established itself as the dominant strain. Comments from Fed Chair Jerome Powell on Wednesday that he and his fellow policymakers will consider at their Dec. 14-15 meeting a faster taper of stimulus, potentially opening the door to earlier interest rate hikes, failed to lift the dollar.