In assessing the second quarter, Moody's noted that other than "several hotspot" virus outbreak areas — which Moody's report didn't name — "the impact and costs of the coronavirus have not been high, and our rated issuers are therefore likely to have a very strong Q2." The rated health care companies included Aetna, now a CVS Health subsidiary, and six publicly traded insurers: Anthem, Centene, Cigna, Humana, Molina and UnitedHealth Group.

"Even if there is a second wave" of COVID-19 coming, said Moody's, "unless it is far worse than this current outbreak, it would also appear to be a small earnings event for the health insurers."

In another insurer bright spot, Moody's said that "given the almost nationwide lockdowns [caused by the virus] just starting to lift, there are much lower levels of accidents, sports injuries, etc." in the second quarter for the insurers to cover.

In a paragraph labeled, "Economic disruption will have mixed effects," Moody's said the nation's surging COVID-19-caused unemployment "will hurt fully insured commercial risk books of health insurers most, because membership will decline." But the unemployment "will benefit the Medicaid and individual market [insurer] businesses, which will gain members," Moody's said.

"The impact on each insurer will depend on business mix," and "Centene and Molina are the most well positioned," the report added.

In assessing 2020's first quarter, Moody's report noted the "slight" increase in first quarter earnings year over year and said EBITDA (earnings before interest, taxes, depreciation and amortization) was up "just 4.5%," and that was because of "higher than expected" medical costs, among other factors.

"The potential impact of the coronavirus dominated the industry's outlook," Moody's also said as it talked about the first quarter. It added that "and all companies stressed tremendous uncertainty about the future, though none revised guidance."

The May 21 report said companies have strengthened "cash positions to deal with potential coronavirus related contingencies," and noted that pursuant to a U.S. Supreme Court ruling the federal government must pay $12.3 billion owed to health insurers under a risk sharing program that was enacted under the Affordable Care Act.

In looking at performance and credit implications for each company, Humana was pointed to as having a particularly strong and "positive view."

Read more: 

• UnitedHealth quarterly earnings a positive sign for health insurers
• The health care industry winners and losers against COVID-19
• Stabilizing insurance premiums amid COVID-19 uncertainty