{description}For most people, coughing and sneezing may rarely be acknowledged beyond a perfunctory “bless you”, but these symptoms are very serious for patients suffering from tuberculosis. Often thought of as a disease of the past, tuberculosis is actually a major health problem in the world today. A Stanford research project recently made progress toward a better understanding of tuberculosis (TB) and multi-drug resistant tuberculosis (MDR-TB). Led by Stanford epidemiologists Gary K. Schoolnik and Peter M. Small (now at the Bill and Melinda Gates Foundation), Associate Professor of Biological Sciences Brendan J. M. Bohannan, former postdoctoral fellow Sebastien Gagneux and graduate student Clara Davis Long, the study examined a long-held belief that bacteria with drug-resistant mutations are at a competitive disadvantage compared to drug-susceptible bacteria. Results of the study, however, revealed that some types of mutations carry no competitive cost. {/description}