The American epidemiologist who led the World Health Organization's vaccination effort that in 1977 wiped out smallpox, one of the world's most feared contagious diseases, has died. Dr. Donald "D.A.'' Henderson was 87 when he died Friday at a hospice care facility in Towson, Maryland, from complications following a hip fracture, Johns Hopkins University said in a statement. Henderson was a former dean of the school's Bloomberg School of Public Health. "D.A. was a force of nature who, until relatively recently, seemed invulnerable. Public health has lost a hero," wrote Michael Klag, current dean of the Bloomberg School. When Henderson, then a 39-year-old epidemiologist, became the first chief of the World Health Organization's smallpox eradication unit in 1967, the virus killed an estimated 2 million people every year on three continents. By the end of his tenure there 10 years later, the disease was all but wiped out worldwide. The WHO certified in 1980 that smallpox had been completely eradicated — a first in human history. After his work for the WHO, Henderson went on to serve as science and bioterrorism adviser to three U.S. presidents, as well as holding other academic and medical posts. He most recently was employed as a distinguished scholar at the University of Pittsburgh Medical Center's Center for Health Security in Baltimore, Maryland. Some information for this report from Reuters.