U.S. insurance stocks retreated after companies across multiple industry segments discussed during first-quarter earnings calls the effects that the COVID-19 pandemic has had on their businesses.

The S&P 500 declined 1.32% for the week ending April 24 to close at 2,836.74, while the SNL U.S. Insurance Index dipped 3.23% to 957.83.

The hardest-hit property and casualty company was RLI Corp., which plunged 21.15%. Employers Holdings Inc., which focuses on workers compensation, dropped 15.59% for the week, while American Financial Group Inc. slid 13.61%.

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Travelers Cos. Inc., down 4.04%; Chubb Ltd., down 12.43%; and W. R. Berkley Corp., down 11.84%, all disclosed losses caused by the pandemic. Chubb's Evan Greenberg also had sharp words regarding attempts to get P&C carriers to pay for certain business-interruption claims.

Wells Fargo analyst Elyse Greenspan said equities are responding to uncertainty caused by the pandemic, adding that the "initial stab at COVID-19 losses" is the most important metric of the first quarter.

"In our minds, it's a combination of having a frame of reference on the size of the potential losses and understanding that this is going to impact numerous business lines throughout the commercial market," Greenspan said in an interview.

RLI's first-quarter earnings results provided one such frame of reference. RBC Capital Markets analyst Mark Dwelle in an email to S&P Global Market Intelligence said the company, which reported a year-over-year loss of $61.3 million, had already received roughly 500 business-interruption claims related to the pandemic.

Dwelle said RLI was not viewed as a company "with potential [business interruption] exposure, which likely prompted either selling or short-selling."

"While we don't think the company's ultimate liability will be all that much, we were surprised at the number of claims already received," he noted.

Progressive Corp. scratched out a modest gain for the week, up 0.45%. Greenspan said P&C carriers with significant personal auto lines like Progressive are the "bright spot" now because of shrinking losses and a drop in miles driven due to stay-at-home restrictions still in effect.

In the life industry, Fitch Ratings revised its outlook for Athene Holding Ltd. and its subsidiaries to negative from stable due to "disruption to economic activity and financial markets" caused by the pandemic and the potential impact of that economic fallout on Athene over the next couple of years.

Athene ended the week down 7.15%. MetLife Inc., up 0.73%, and Lincoln National Corp., up 1.85%, were among the better performers in the life insurance sector.

Everest Re Group Ltd. said its first-quarter results will include $150 million in pretax net first-party losses for anticipated pandemic-related claims, which Greenspan said in a note was primarily in its reinsurance segment. The reinsurer finished the week down 13.01%.

Most health insurance-related companies suffered mild losses, except for online marketplace eHealth Inc., which plummeted 14.51% amid ongoing accusations of improper accounting practices leveled by Muddy Waters, and a class-action lawsuit.