Smallpox infection. Historically the survival rate of smallpox varied, but in most communities there was a fatality rate (chance of death) of about 30-35%. The last natural case in the world was in 1975 or 1977 depending on which form you are talking about, and the last case of an infected individual was in 1978 in a laboratory, so you are unlikely to have to worry about getting infected by this.
Depends/presentation. In general, smallpox had a case fatality rate of 30%. More malignant or hemorragic presentations had death rates approaching 100%. Treatments during the 30+ years ago when cases were seen were supportive. Some newer antiviral meds might be of use but their value is unknown.