Infectious diseases are caused by pathogenic micro-organisms — germs — that enter the body, multiply and cause illness. The primary agents include viruses (e.g. COVID-19), bacteria (e.g. strep throat), fungi (e.g. ringworm), and parasites (e.g. Malaria). These pathogens spread through direct contact, airborne droplets, contaminated food/water, or vectors like insects.
Types of Pathogens
| Type | Description | Examples |
| <strong>Viruses</strong> | Tiny organisms that hijack cells to multiply | AIDS, Chickenpox, Common Cold |
| <strong>Bacteria</strong> | Single-celled organisms causing infections | Strep throat, UTIs, Tuberculosis |
| <strong>Fungi</strong> | Organisms causing skin and systemic infections | Athlete’s foot, Ringworm |
| <strong>Parasites</strong> | Organisms living on or in a host | Malaria (protozoa), Tapeworms |
| <strong>Prions</strong> | Rare infectious protein particles | Creutzfeldt-Jakob disease |
Conclusion
Infectious diseases share a single cause: pathogenic microbes (viruses, bacteria, fungi, parasites, or prions) entering the body and replicating. Knowing the type of pathogen and how it spreads is the basis for prevention, treatment, and control.
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