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 deluxe edition for "Record Collector", journalist Joel McIver eulogized it as a "masterpiece of technical, melodic thrash" and a showcase of Megadeth "at their best and most coherent". "Countdown to Extinction" was released on July 6, 1992 through Capitol Records and debuted at number two on the "Billboard" 200 with first week sales of 128,000 copies. It was prevented from entering the chart at number one because of Billy Ray Cyrus' long chart-topping reign with "Some Gave All". The album was acknowledged as the band's commercial breakthrough, and according to authors Pete Prown and Harvey P. Newquist, Megadeth "reached the