Tuberculosis is not a terribly widespread disease in the United States — it afflicted roughly six in 100,000 Americans during one recent 10-year period — but it remains a deadly illness, particularly for people with HIV/AIDS, and eradication efforts have shown it to be a stubborn one too. Texas has the second-largest TB population in the country, and from 1995 to 2004, a Houston-based group of researchers conducted a detailed study of the disease called the Houston Tuberculosis Initiative. Whereas previous efforts looked at city-wide disease rates en masse, the new initiative aimed to identify more precise patterns of transmission within the region.
The Houston Tuberculosis Initiative targeted a number of predictable risk factors associated with the distribution of endemic TB, including income, race and history of homelessness. It also found one rather surprising link: use of public transportation.