Diagnostic Uncertainty, Microbes, and the Isolation of People with Cystic Fibrosis

The framing of cystic fibrosis (CF) changed from a strictly genetic disease in the midto late-twentieth century to a genetic/infectious hybrid of sorts by the early twentyfirst century, providing an opportunity to examine the nature of disease definition in medicine. Respiratory infections had long been associated with CF, yet it was not until the late twentieth century that many physicians became concerned about the possibility of patient-to-patient transmission of a particularly pathogenic microorganism. Initially termed Pseudomonas cepacia, the microbe was linked to rapid decline and even death in some people with CF, and early efforts to prevent its spread included the segregation of infected individuals. However, soon after segregation was implemented in a range of medical and social contexts, physicians began to suspect that people with CF did not always test positive for P. cepacia in the setting of infection, due to challenges isolating and identifying the microorganism in the laboratory. These sources of diagnostic uncertainty, coupled with the severe health outcomes associated with P. cepacia infection, prompted those in leadership positions to treat all people with CF as a potential source of contagion and restrict their in-person interactions, a practice that has had a profound impact on the CF community.