Dallas Stars will be without star defenceman for some time as he is out indefinitely

Mononucleosis is an illness that commonly affects teenagers and young adults, but can affect children as well. Viruses, most commonly Epstein-Barr Virus (EBV), and certain infections cause the illness. Mono is sometimes called «the kissing disease» because it spreads easily through bodily fluids like saliva.

For most people, mono isn't serious, and it improves without treatment. Still, extreme fatigue, body aches and other symptoms can interfere with school, work and daily life. With mono, you might feel sick for about a month.
- From my.clevelandclinic.org