He is the J. H. Kempner Professor of human genetics at the University of Texas medical school in Galveston, Texas, USA. His group developed the first infectious clones of an epidemic strain of West Nile virus and zika virus, discovered two RNA methylation activities of the cap protein of flavivirus NS5, identified the main RNA elements for flavivirus replication, created various platforms for the discovery of flavivirus vaccines and drugs, and pioneered the development of therapeutics for Dengue virus.