Pandemic smallpox was responsible for 300–500 million deaths. As recently as the early 1950s, an estimated 50 million cases of smallpox occurred in the world each year. After successful vaccination campaigns throughout the 19th and 20th centuries, the WHO certified the eradication of smallpox in December 1979. To this day, smallpox is the only human infectious disease to have been completely eradicated, and one of two infectious viruses ever to be eradicated. Historically, measles was prevalent throughout the world, as it is highly contagious. According to the U.S. National Immunization Program, 90% of people were infected with measles by age 15.
Countdown to Extinction Countdown to Extinction Countdown to Extinction is the fifth studio album by American thrash metal band Megadeth, released on July 14, 1992, through Capitol Records. It was the group's second studio release to feature the "classic" lineup of Dave Mustaine, Marty Friedman, David Ellefson and Nick Menza, with all of them contributing to songwriting on the album. The album features some of the band's best known songs such as "Symphony of Destruction", "Sweating Bullets" and "Skin o' My Teeth", which enjoyed significant chart success and made a great musical impact. "Countdown to Extinction" received positive reaction from music critics, who