11/06/2026
pathogens (disease-causing agents), classifying them into different groups: Viruses, Bacteria, Fungi, Protozoa, Parasites, and Proteins.
🔹 What are Pathogens?
Definition: Any agent that causes disease.
Usually a living microorganism capable of producing infection.
Excludes non-living poisons like arsenic (chemical toxins).
Pathogens are categorized based on their structure, nature, and mode of infection.
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1. VIRUSES
Nature: Not truly living (need a host to reproduce).
Structure: Genetic material (DNA or RNA) surrounded by a protein coat.
Reproduction: Can only multiply inside a living cell (plant, animal, human).
Diseases caused:
Hepatitis
Herpes, Mononucleosis
Warts
Chickenpox, Smallpox
Bird flu (H5N1)
Norovirus
Yellow fever, Ebola
SARS
AIDS/HIV
Influenza (Flu)
Cold sores, Cold germs
Measles, Tetanus
Typhoid (rarely viral but mentioned here)
Transmission: Airborne droplets, blood, body fluids, contact.
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2. BACTERIA
Nature: Tiny one-celled microorganisms.
Living: Can survive inside or outside the body.
Reproduction: Asexual (binary fission).
Diseases caused:
Tuberculosis
Pneumonia
Anthrax
Staphylococcus (Staph infection)
E. coli infections
Typhoid
Salmonella (food poisoning)
Urinary Tract Infection (UTI)
Peritonitis
Strep throat
Stomach ulcers (e.g., H. pylori)
Tularemia
Lyme disease
Transmission: Contaminated food, water, contact, or vectors.
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3. FUNGI
Nature: Multi-celled, plant-like organisms (but not plants).
Nutrition: Absorb nutrients from plants, trees, or animals.
Diseases caused:
Ringworm (skin infection)
Advanced Pneumonia (fungal type)
Candidiasis (Candida yeast infection)
Yeast infection
Histoplasmosis
Cryptococcosis
Transmission: Spores in the air, contaminated soil, or surfaces.
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4. PROTOZOA
Nature: Single-celled eukaryotic organisms.
Habitat: Often live in water; many are parasites.
Diseases caused:
Malaria (Plasmodium via mosquito)
Chagas disease
Giardiasis
Cryptosporidiosis
Transmission: Insect bites, contaminated water, or food.
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5. PARASITES
Nature: Complex living organisms.
Survival: Live in the intestinal tract or bloodstream of a host.
Diseases caused:
Roundworm infection
Tapeworm infection
Trichinosis (from undercooked pork)
Morgellons (debated condition, sometimes linked to parasites)
Transmission: Contaminated food, water, soil, or vectors.
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6. PROTEINS (Prions)
Nature: Misfolded proteins (not living organisms).
Unique feature: Do not contain DNA or RNA, but still infectious.
Diseases caused:
Bovine Spongiform Encephalopathy (BSE, "Mad Cow Disease")
vCJD (Variant Creutzfeldt–Jakob Disease)
Transmission: Contaminated meat, medical procedures.
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📌 Summary
Viruses → Need host cells, cause flu, HIV, Ebola.
Bacteria → One-celled, cause TB, UTIs, food poisoning.
Fungi → Plant-like, cause skin & lung infections.
Protozoa → Single-celled, waterborne or vector-borne (e.g., malaria).
Parasites → Multicellular, live in intestines/blood (worms).
Proteins (Prions) → Infectious proteins, cause brain diseases.See more.. 🩺🧑🏻⚕️🖼️👇🏻
