Figure 2. Association of human parvovirus B-19 with erythema infectiosum by immuno electron microscopic. A. Airfuge EM-90 rotor (Beckman, Palo Alto, CA) preparation of human serum prospectively collected at time of contact with case of erythema infectiosum. Erythema infectiosum-like rash developed 1 week after collection of serum. B. Immuno electron microscopic preparation of the serum in panel A. The serum was mixed with matched convalescent-phase serum (final dilution convalescent-phase serum 1:100), incubated for 90 min at 37°C, and virions/immune complexes centrifuged directly to a specimen grid with the EM-90 rotor. Arrow, complete virion, arrowhead, genome defective virion. phosphotungstic acid. Bar = 100 nm. For study details, see Plummer et al., 1985 (16).