A powerful technique can be the use of immunolabelling procedures followed by negative staining on virus particles.
See: Spehner, D., R. Drillien, F. Proamer, C. Houssais-Pecheur, M. A. Zanta, M. Geist, K.Dott, and J. M. Balloul, Virology 273:9-15 (2000).
