Dr. Parsonnet specializes in adult infectious diseases. She has a particular interest in gastrointestinal infections, including H. pylori infection and diarrheal diseases, tuberculosis and illnesses with prolonged fever. Dr. Parsonnet also has an active research enterprise in which she studies the way infections contribute to the development of chronic diseases including cancer, allergy and obesity. She has had continuous funding from the National Institutes of Health for over 25 years and has served as a member of numerous advisory boards, professional societies, and scientific review committees.