(Reuters) - Britain's FTSE 100 lost steam on Wednesday, as rising global deaths doused hopes that the coronavirus crisis was abating, while insurers took a hit over halts in dividend payments and Tesco warned of a surge in costs.The blue-chip FTSE 100 index fell 1.8% after closing at a near two-week high on Tuesday. It is still up 3.6% for the week. Shares of Aviva Plc and Direct Line , RSA and Lloyds of London-member Hiscox fell between 2.4% and 8.3% after saying they were cancelling 2019..