In April 1980 Meselson served as a resident consultant to the CIA investigating a major outbreak of anthrax among people in the Soviet city of Sverdlovsk. He concluded that on the basis of available evidence the official Soviet explanation that the outbreak was caused by consumption of meat from infected cattle was plausible but that there should be an independent on-site investigation. After the collapse of the Soviet Union, he was allowed to bring a team to Sverdlovsk in 1992 and again in 1993. Their reports conclusively showed that the official Soviet explanation was wrong and that the outbreak was caused by the release of an anthrax aerosol at a military biological facility in the city.