After enduring historic sell-offs over the last month, equity markets put together one of their best weeks in decades as Congress took action on a pandemic rescue package.

Despite a sharp decline in the final day of trading for the week of March 27, the S&P 500 still rose 10.26% to 2,541.47, while the SNL U.S. Insurance Index jumped 17.50% to 911.55.

The U.S. Senate announced midweek that it had reached an agreement on a $2 trillion economic relief bill to help combat the impact of the coronavirus pandemic. The package included financial assistance for hospitals, the healthcare industry and small businesses, a huge boost to unemployment insurance benefits and direct cash payments to most Americans. That bill was approved by the House of Representatives on March 27.

In the life insurance space, Athene Holding Ltd. held a special conference call during which company executives said the COVID-19 crisis and the market volatility it has caused had not derailed ongoing M&A discussions. Chairman and CEO James Belardi told investors that "while today's environment will leave no corner of the financial world untouched," the company is "well-prepared."

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After being punished for the better part of a month, Athene's stock soared this week, closing up 53.65%.

"I think the stimulus itself probably served to quell the concern about a rash of corporate bankruptcies," Piper Sandler analyst John Barnidge said in an interview. "Given that, and Athene's business update call on their investment portfolio earlier this week, I think they definitely served to quell some level of investor concerns around that topic, at least for the week."

Many other major life insurance companies saw their stocks rise by at least 20%. Lincoln National Corp., which had been one of the 15 worst performers among S&P 500 companies since Feb. 28, soared 60.96% this week. Unum Group climbed 51.23%, National Western Life Group Inc. rose 32.08%, Aflac Inc. added 32.44%, MetLife Inc. gained 26.62% and Prudential Financial Inc. jumped 25.51%.

Barnidge would not say if this week's gains marked the end of the brutal selling that has hit stocks across the board over the last month. Though there have been "fits and starts," the analyst said progress is being made on the "fiscal and monetary front."

"Ultimately, this is a health crisis, so we have to let that play out a little bit," he added.

S&P Global Ratings this week said it is maintaining its "stable outlook" for North American life insurers. The industry's "robust capital and liquidity" should help it deal with the shock being caused by social distancing measures and the ongoing energy sector crisis, the rating agency said.

Keefe Bruyette and Woods analyst Ryan Krueger in a note said the mortality risk in the life sector is in permanent life insurance, term life and group life. COVID-19 is primarily affecting the elderly and people with pre-existing conditions, with about 80% of deaths concentrated in adults 65 and older, he noted. That makes it less risky for term life and group life products where KBW estimates an average in-force policyholder being in their mid-to-late 40s.

The rescue bill also got a thumbs-up in a note from Cantor Fitzgerald analyst Steven Halper, who called it "a net positive" for managed care companies. While the hospital industry will be a significant beneficiary of the package, Medicare Advantage plans will benefit as well because it suspends sequestration spending reductions that had been included in their rate calculations.

Humana Inc. was the biggest winner in the health insurance space as its share price finished up 28.82% for the week. Other big gainers in the managed care space included UnitedHealth Group Inc., up 17.36%, and Molina Healthcare Inc., up 18.83%.

Anthem Inc. also scored big gains this week despite being sued for alleged Medicare fraud. It closed up 16.37%.

Leading the property and casualty segment this week were State Auto Financial Corp., up 35.80%; Kemper Corp., up 21.52%; and Allstate Corp., up 19.75%.

Also this week, Chubb Ltd., which is a major player in cyber insurance, said it was investigating a "computer security incident" that may involve unauthorized access to data held by a third-party service provider.

A spokesperson for Chubb, which finished the week higher by 6.74%, said it had no evidence the incident affected its network, which "remains fully operational."