Research on virology has been performed at the institute since it was founded, and this resulted in the first description of a lentivirus, the MVV (Maedi-Visna Virus), a pioneering work by Björn Sigurdsson and collaborators. His major breakthroughs were on the introduction of the concept of slow viral infections, still well accepted and now referred to as the legacy of Dr. Björn Sigurdsson. The striking feature that Sigurdsson discovered is the slow progression to disease after primary infection. He developed a framework of experimentation for studying the slow and usually progressive and fatal brain infections. Sigurdsson presented originally his theory on atypical slow infections in a series of lectures at the University of London in the year of 1954. Together with his collaborators they managed to grow MVV in vitro, the first in vitro growth of a lentivirus.
Today the work on virology at the institute is still focused on MVV, but also on other viruses. Several disciplines are utilized in the research projects, including molecular methods for the last decades. Both viral (vif and others) and cellular proteins (APOBEC and others) involved in the life cycle of the virus are investigated. In addition to research projects on MVV, there are ongoing projects on herpesviruses in horses. Several aspects of the research projects in virology are based on international collaboration