Smallpox is a highly infectious disease caused by the variola virus, which claimed the lives of 300 million people in the 20th century.
Several vials that were labelled «smallpox» and accidentally found at a laboratory in the US state of Pennsylvania raised the alarm for threats of a virus leak to public health, local media has reported. A laboratory worker found 15 vials while cleaning out a freezer in a facility that conducts vaccine research outside Philadelphia, with five labelled «smallpox» and 10 as «vaccinia», Xinhua news agency reported.
