Research Driven by Curiosity: The Journey from Basic Molecular Biology and Virology to Studies of Human Pathogenic Coronaviruses

The second major discovery was that another type of T cell, the CD4 T cell, was the major factor in host tissue damage in MHV-infected mice, and that virus-specific CD4 T cells were responsible for much of the tissue destruction and clinical disease. [...]the early 2000s, coronaviruses were not considered important human pathogens.