The healthcare insurance and services company posted strong growth numbers, due largely to growth in total premiums, although a cyberattack affected its results.It's still early days in this latest earnings season, but it seems we can already tag one winner in the healthcare sector -- take a bow, UnitedHealth Group (UNH 0.30%).As the season lurched into action, the sprawling healthcare insurer and services provider published its first-quarter results. These not only showed very encouraging growth dynamics i ...