Infectious Diseases — Core Principles
Core Principles
Infectious diseases are illnesses caused by tiny invaders called pathogens, which include viruses, bacteria, fungi, and parasites. These pathogens enter the body, multiply, and cause harm, leading to symptoms like fever, cough, or pain.
What defines them is their ability to spread from one individual to another, or from an environment to a person. This spread, known as transmission, can occur directly through contact or droplets, or indirectly via contaminated food, water, objects (fomites), or living carriers like mosquitoes (vectors).
Common examples in humans include bacterial diseases like Typhoid and Pneumonia, viral diseases like the Common Cold and AIDS, protozoan diseases such as Malaria and Amoebiasis, and helminthic infections like Ascariasis and Filariasis.
Fungal infections like Ringworm also fall into this category. Each disease has a specific causative agent, mode of transmission, characteristic symptoms, and targeted prevention and treatment strategies.
Prevention often involves vaccination, good hygiene, sanitation, and vector control, while treatment varies from antibiotics for bacterial infections to antivirals for viral ones. Understanding these basics is fundamental to preventing and managing infectious diseases.
Important Differences
vs Non-infectious Diseases
| Aspect | This Topic | Non-infectious Diseases |
|---|---|---|
| Causative Agent | Pathogens (viruses, bacteria, fungi, parasites) | Genetic factors, lifestyle choices, environmental factors, nutritional deficiencies, aging, organ dysfunction |
| Transmission | Transmissible from person to person, animal to person, or environment to person (direct/indirect) | Generally not transmissible from one individual to another |
| Examples | Common cold, flu, malaria, typhoid, AIDS, tuberculosis | Diabetes, heart disease, cancer (most forms), asthma, genetic disorders, nutritional deficiencies (e.g., scurvy) |
| Prevention Strategies | Vaccination, hygiene, sanitation, vector control, safe practices (e.g., safe sex) | Healthy lifestyle (diet, exercise), avoiding risk factors (smoking, pollution), genetic counseling, regular health check-ups |
| Immune System Role | Immune system actively fights off pathogens; immunity can be developed | Immune system may be involved in autoimmune diseases, but not in fighting an external pathogen |