User lamethunder started a thread on the official subreddit for discussion of "Chicago Med" titled "Why does no one find April's TB weird?" referring to a reveal in the Season 1 finale that April is positive for tuberculosis. They then explained that they believe TB to be highly uncommon, whereas the characters that find out about April's diagnosis treat it as nothing outside the ordinary.
In response, a number of users shared anecdotal statistics about TB and its prevalence in the present day. One user specifically mentioned that incidences of TB are higher among healthcare workers. A study published by The National Center for Biotechnology Information corroborates this, claiming that "[healthcare workers] are at higher than average risk for TB. Sound TB infection control measures should be implemented in all health care facilities with patients suspected of having infectious TB."
That said, the CDC reported a total of 7,860 cases of TB in the USA during 2021. In effect, then, the original poster has some statistical basis for their inquiry — even adjusting for a higher prevalence among healthcare workers, TB does indeed appear to be exceedingly rare. Nevertheless, April's coworkers may simply treat even rare medical conditions as a fact of life due to their line of work, hence their matter-of-factness.
