Flu season may have a more muted impact on some healthcare stocks than investors expect, even though experts warn that this year's version is shaping up to be more intense than recent seasons.

Higher-than-normal reports of flu started cropping up in several states before Christmas, and flu-related hospitalizations also began climbing earlier than usual. The Centers for Disease Control and Prevention has warned that they see a bad season shaping up for the flu, which usually peaks in midwinter.

On average, about 24,000 Americans die each flu season, according to the CDC.

"The current cold, cough and flu season looks to be the most severe in at least the last decade and continues to intensify," analyst Edward J. Kelly said in a research note. Kelly covers pharmacies for Credit Suisse.

Flu season can help revenue for drugstore chains like Walgreen Co., CVS Caremark Corp. or Rite Aid Corp. because it brings more patients to stores to fill prescriptions or pick up disinfectants or over-the-counter symptom remedies.

Kelly said an analysis of the three most severe flu seasons in the last decade shows that drugstore stocks perform well as flu activity picks up, but they then give back much of the gain in the following months.

"Given the strong performance of the sector since the flu season began in November, it seems like this catalyst may already be priced into the stocks," Kelly wrote.

Shares of several health insurers slipped Tuesday, and Bernstein analyst Ana Gupte said in a separate note fear about the flu season's intensity may have pushed the sector down.

Investors worry that a spike in flu claims can chip away at insurer profitability, especially in last year's fourth quarter and this year's first quarter. But Gupte said the share sell-off was overdone, and worst-case flu scenarios would be manageable for big, diversified health insurers like Aetna Inc. or UnitedHealth Group Inc.

Aetna Chairman and CEO Mark Bertolini said Tuesday his company has seen a spike in flu intensity following two very mild seasons. But that has been moderated by fewer hospital admissions than the insurer saw in other flu seasons. Bertolini said the insurer expects to spend between $40 million and $50 million on flu claims this season, which is a normal range.

In contrast, the company spent $100 million in the swine flu season of 2009.
"We don't see this flu season, even at its worst, getting close to that number," Bertolini said during an appearance at J.P. Morgan's annual healthcare conference in San Francisco.

In morning trading Wednesday, shares of Aetna rose 90 cents, or 2 percent, to $45.28; UnitedHealth gained 50 cents to $51.90; and another health insurer, WellPoint Inc., added 13 cents to $60.21. Among drugstore operators, Walgreen shares rose 12 cents to $38.29; CVS Caremark rose 28 cents to $50.13 and Rite Aid rose 5 cents to $1.38.

Meanwhile, the Standard & Poor's 500 index climbed less than 1 percent.