patogenens

Patogenens (pathogens) are biological agents capable of causing disease in a host. They include bacteria, viruses, fungi, parasites such as protozoa and helminths, and prions. Some patogenens require living tissue to replicate; others can reproduce outside a host or within vectors.

Pathogens vary in their biology and in how they cause illness. Bacteria such as Mycobacterium tuberculosis, viruses such as influenza, fungi such as Candida species, protozoan parasites such as Plasmodium, helminths such as schistosomes, and prions such as those associated with Creutzfeldt–Jakob disease represent major groups.

Transmission routes include inhalation, ingestion, direct contact, sexual contact, contaminated surfaces, and vectors. After entry, pathogens interact with host tissues, sometimes evading immune defenses, producing toxins, or damaging cells. The severity of disease depends on pathogen virulence, infectious dose, and host factors like immunity, age, and comorbidities.

Pathogenicity is influenced by virulence factors such as adhesion molecules, invasive enzymes, toxins, and immune evasion strategies. Some organisms are opportunistic pathogens, causing disease mainly when host defenses are weakened. Others are primary pathogens capable of causing disease in healthy individuals.

Detection and diagnosis rely on culture, microscopy, molecular methods, serology, and sequencing, complemented by clinical assessment. Prevention and control include vaccination, aseptic technique, hygiene, safe food and water, vector control, antimicrobial stewardship, and public health surveillance. The emergence of new patogenens and antimicrobial resistance remains a global concern.