SAN CLEMENTE, Calif. (AP) — Paul F. Wehrle, an infectious and communicable diseases expert who helped wipe out smallpox, has died at age 82.

Wehrle died Tuesday of natural causes, his son Karl Wehrle said on Sunday.

Wehrle helped develop the vaccination that led the World Health Organization to declare smallpox eradicated in 1980. In the 1960s as a medical officer for the WHO, he traveled to Nepal, India, Africa, South America and Afghanistan to administer the vaccine.

Wehrle also worked on the clinical trials for the Salk vaccine, which wiped out polio. First administered in 1954, the vaccine was named for its chief developer, Dr. Jonas Salk.