Pathogenese

Pathogenesis, or Pathogenese, is the set of biological mechanisms that lead from exposure to a pathogenic organism to the development of disease in a host. It integrates factors related to the pathogen, the host, and the environment. Pathogenesis is distinct from etiology (the cause) and from pathophysiology (the functional changes that accompany disease).

The sequence typically includes entry, adherence, colonization, invasion or dissemination within the host, replication, and tissue damage, followed by clinical symptoms. Pathogens deploy virulence factors such as adhesins, invasins, toxins, capsules, immune evasion strategies, and methods to manipulate host signaling. The host's immune response can contribute to tissue injury and symptoms.

Pathogens vary by type, including bacteria, viruses, fungi, parasites, and prions. Outcomes range from localized infection to systemic illness, chronic disease, latency, or oncogenic processes. In some cases the disease results from toxin-mediated damage rather than direct invasion.

Factors influencing pathogenesis include inoculum size, route of entry, tissue tropism, and the local environment, as well as host factors such as age, nutrition, genetics, vaccination status, and immunocompetence. The microbiome and prior immunity can modify the course of infection.

Studying pathogenesis supports prevention, diagnosis, and treatment. It informs vaccine design, antimicrobial strategies, and public health interventions. Traditional concepts such as Koch's postulates have evolved with molecular methods to identify virulence determinants and host pathways involved in disease.