Steffen is an Applied Mathematician broadly interested in understanding the mechanisms underlying diseases. His current research is on the growth and persistence of pathogens within a host and immune responses towards these pathogens. The primary pathogens he focuses on are HIV and Simian Immunodeficiency Virus (SIV), but Steffen has also worked on Malaria and COVID-19. In his research, Steffen works closely with experimental collaborators from the fields of virology and immunology.
Previously, Steffen's dissertation research focused on modelling the effects of anti-arrhythmic drugs on electrical signalling in the heart, which he completed at the University of California, Davis, receiving his Ph.D. in applied mathematics in 2018.