The people infected two students working National Institute Virology Laboratory relatives.There almost 30 BL4 laboratories listed worldwide.Their operations always source controversy suspicion , particular previously involved manufacture biological weapons.With signing 1972 Convention Prohibition Biological Weapons , banned development , acquisition , stockpiling use biological weapons , purpose laboratories changed.They officially work fight epidemics biological weapons.However , shown certain countries , including former Soviet Union , continued fund biological-weapons research programs , Biopreparat , despite signed convention.These BL4 laboratories indeed already linked accidents.For example , 1979 Sverdlovsk disaster , involved accidental spread spores bacterium Bacillus anthracis causes anthrax , caused dozens deaths .