The classification of infectious diseases relies not solely on objective signs, but also on patient-reported symptoms and diagnostic methods that confirm the pathogen involved.
The statement that the classification of infectious diseases is based on observable changes in the body, such as fever, sounds, and increased cell counts, making it objective is false. Infectious diseases are indeed often identified by observable signs, which are objective and measurable phenomena, such as a fever or an increased white blood cell count. However, the classification and diagnosis of infectious diseases also consider symptoms, which are subjective and reported by the patient, such as pain or fatigue.
Furthermore, diagnosing an infectious disease often requires direct and indirect diagnostic methods beyond just the observation of signs and symptoms, like cultures, microscopic examination, serological tests, and biochemical tests, to confirm the identity of the pathogen responsible.