False about period of pathogenesis is:
|A||Screening has no role|
|B||Begins with entry of disease agent in the susceptible host|
|C||May be modified by immunization and chemotherapy|
|D||Hosts reaction to infection is not predictable|
Pathogenesis phase –
1. The pathogenesis phase begins with the entry of the disease "agent" in the susceptible human host. The further events in the pathogenesis phase are clear-cut in infectious diseases, i.e., the disease. agent multiplies and induces tissue and physiological changes, the disease progresses through a period of incubation and later through early and late pathogenesis. The final outcome of the disease may be recovery, disability or death. The pathogenesis phase may be modified by intervention measures such as immunization and chemotherapy.
2. It is useful to remember at this stage that the host's reaction to infection with a disease agent is not predictable. That is, the infection may be clinical or sub-clinical; typical or atypical or the host may become a carrier with or without having developed clinical disease as in the case of diphtheria and poliomyelitis.
3. In chronic diseases (e.g., coronary heart disease, hypertension, cancer), the early pathogenesis phase is less dramatic. This phase in chronic diseases is referred to as presymptomatic phase. During the presymptomatic stage, there is no manifest disease. The pathological changes are essentially below the level of the "clinical horizon". The clinical stage begins when recognizable signs or symptoms appear. By the time signs and symptoms appear, the disease phase is already well advanced into the late pathogenesis phase. In many chronic diseases, the agent-host-environmental interactions are not yet well understood.