There is a very good FAQ on this forum about medical insurance in Switzerland.

Just to clarify some points : Swiss medical insurance companies are non-profit making. For the basic insurance they have to accept you irrespective of pre-existing medical conditions. They cannot load the premium or terminate the cover because you are a bad risk. The basic insurance includes cover for emergency treatment while abroad – see this and click on 1.4 Cover Abroad. As this suggests it’s just for emergencies and not for routine treatment.