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.

Wehrle was chairman of the University of Southern California's pediatrics department from 1961 to 1988 and published numerous academic articles and books on infectious and communicable diseases.

Wehrle also did research on the effects of air pollution on people and served as a member of the Air Pollution Training Committee of the U.S. Public Health Service.

Before arriving at USC in 1961, Wehrle taught at the universities of Illinois and Pittsburgh, Johns Hopkins University and State University of New York. After retiring from USC in 1988, he served two years as interim chairman of pediatrics at the University of California, Irvine.

Besides son Karl, survivors include Wehrle's wife, Beth, three other sons, a sister and 12 grandchildren.