Particles associated with Australia antigen in the sera of patients with leukemia, Down's syndrome and hepatitis.

Particles with the appearance of a virus were detected by electron microscopy in the serum of individuals with Au. These were subsequently shown to be the surface antigen particles, different from the whole virus particles. Blumberg's discovery of the Australia antigen in 1965 may technically be considered the discovery of the hepatitis B virus, but at the time of that discovery its connection with a virus was speculative.