Lloyd's of London is likely to pay out $3-4.3 billion in insurance claims related to the coronavirus pandemic, similar to losses from the 9/11 attacks, it said today.
The pandemic has locked down economies around the world, bringing businesses, events and travel to a halt and leading to hefty claims.
Global non-life underwriting and investment losses may hit a record $203 billion in 2020, the commercial insurance market added.
Zurich Insurance also said today it expected $750m in non-life pandemic claims this year.
In a double blow, insurers have also lost money due to falling markets, slashing the investments they use to pay out claims.
"I don't think anyone in our industry has ever seen both happen at once," Lloyd's chief executive John Neal told Reuters.
Investment losses were seen at $96 billion.
Global insured loss forecasts of $107 billion are similar to natural catastrophe losses in 2005 led by Hurricanes Katrina, Rita and Wilma and to 2017 including Hurricanes Harvey, Irma and Maria, Lloyd's said.
Lloyd's' estimates do not include life insurance and assume continuing social distancing and lockdown measures in 2020, as well as a drop in global GDP.
The bulk of the insurance losses come from cancellation or postponement of major events around the world including the Olympics, business interruption claims on property insurance and trade credit.
Small businesses in Britain are battling insurers who they say have denied them payments for disruption. The insurers say most small business policies do not cover the pandemic.
Lloyd's of London insurer Hiscox is one of those under scrutiny.
Neal said the UK domestic property sector accounted for less than 2% of the Lloyd's market, adding that "any valid claims should be paid".
Life insurers are also being hit by the crisis, particularly as lockdown measures prevent agents from meeting customers. Prudential said today its Asia first-quarter sales were down 24% and it expected a challenging second quarter.
But the crisis is also throwing up opportunities for new products. Lloyd's is insuring clinical trials and is considering "Recover Re" after-the-event long-term insurance to help businesses recover from pandemics, including Covid-19.
The underwriting floor at Lloyd's, a focal point for the market which employs nearly 50,000 people, was unlikely to open before August, Neal said.
But some of Lloyd's' own staff could start returning to its City of London tower in June, he added.