The boundary between contagious and non-contagious infectious diseases is not perfectly drawn, as illustrated classically by tuberculosis, which is clearly transmissible from person to person, but was not classically considered a contagious disease.
A fronteira entre as doenzas contaxiosas transmisibles e non transmisibles non está perfectamente debuxada, como o ilustra o caso clásico da tuberculose, que é claramente transmisible de persoa a persoa pero polo xeral non é considerada unha enfermidade contaxiosa.