On Tuesday, UnitedHealth cast a pall over the health insurance sector after issuing a profit warning for the full year. The blow was made all the more painful by the fact that the company justified the downgrade by citing business disruptions linked to the major cyber-attack earlier in the year. However, the company had repeatedly reassured investors about this event.

Now it's Elevance Health 's turn to scare shareholders. The company plunged 14% after lowering its earnings per share expectations from $37.2 to $33 following lower-than-expected quarterly results. This is the stock's biggest daily decline since March 2020.

Elevance Health specializes in the Medicaid segment, a healthcare program for low-income individuals. In contrast, the other flagship health insurance program in the United States is Medicare. It is aimed at people over 65, as well as those with specific disabilities and illnesses.

Elevance Health reveals "unprecedented challenges" in its Medicaid business. In its fall, Elevance Health drags Centene (-10%) and Molina (-12%), two players who generate most of their revenues in this segment.