Chest X ray from a tuberculosis patient (Image Lynne Sladky, Associated Press)
Several weeks ago a high school student in Kansas was diagnosed with active tuberculosis, a disease characterized by cough, fever, night sweats, and wasting. Active TB patients are capable of transmitting the infection to others, but those others typically do not become sick right away. The TB bacteria infect their lungs in a dormant state, termed latent infection. These individuals are not contagious; the bacteria are sequestered in their lungs, and they are not coughing to facilitate its transmission.
TB bacteria sequestration in lungs during latent infection L. Ramakrishnan, Nature Reviews Immunology 12: 352-366, 2012
As it turns out, the first student has infected 27 others, who are now in the latent stage of the disease. Those students are not contagious. All 28 persons are currently undergoing antibiotic treatment, and are expected to recover fully without infecting anyone else. How frightening is it that there are 28 tuberculosis patients in Kansas? It is actually quite a normal level. We do not tend to hear about it, but TB is not spectacularly unusual in the least.
As we just learned with Ebola, assessment of risk to others is well-understood. Nothing to worry about here.