Evolution of viruses, and evolution of bacteria. My research employs computer analyses of nucleotide and protein sequence data to address a range of evolutionary questions.

Viral evolution: what are the origins of human viruses, and what factors influence their genetic diversity? A particular focus has been the origins and evolution of AIDS viruses.

Bacterial evolution: what do bacterial genome sequences tell us about evolution? Two particular areas involve the evolution of synonymous codon usage bias, and the evolution of repetitive sequence families.