### Definition of Pathogens
Pathogens are microorganisms that cause disease in their host. These can be bacteria, viruses, fungi, protozoa, prions, or parasitic worms. They invade the body and create disturbances that result in illness.
### Six Types of Pathogens and Three Examples of Each
1. **Bacteria**
Bacteria are single-celled organisms that can thrive in a variety of environments.
- **Examples:**
- *Escherichia coli* (E. coli): Often causes food poisoning.
- *Streptococcus pneumoniae*: Causes pneumonia.
- *Mycobacterium tuberculosis*: Causes tuberculosis.
2. **Viruses**
Viruses are tiny infectious agents that can only replicate inside the living cells of an organism.
- **Examples:**
- Influenza virus: Causes the flu.
- Human Immunodeficiency Virus (HIV): Causes AIDS.
- SARS-CoV-2: Causes COVID-19.
3. **Fungi**
Fungi can be single-celled or multi-celled organisms and include yeasts and molds.
- **Examples:**
- *Candida albicans*: Causes yeast infections.
- *Aspergillus fumigatus*: Can cause aspergillosis, especially in immunocompromised individuals.
- *Tinea corporis*: Causes ringworm.
4. **Protozoa**
Protozoa are single-celled organisms that often inhabit water or moist environments.
- **Examples:**
- *Plasmodium falciparum*: Causes malaria.
- *Giardia lamblia*: Causes giardiasis.
- *Entamoeba histolytica*: Causes amoebiasis.
5. **Prions**
Prions are misfolded proteins that can induce other proteins to misfold, leading to disease.
- **Examples:**
- Creutzfeldt-Jakob disease (CJD)
- Bovine spongiform encephalopathy (BSE or "mad cow disease")
- Kuru (associated with cannibalistic practices)
6. **Parasitic Worms (Helminths)**
These are large, multicellular organisms that can live inside or on the host.
- **Examples:**
- *Ascaris lumbricoides*: Causes ascariasis.
- *Taenia solium*: Known as the pork tapeworm, causes taeniasis.
- *Schistosoma mansoni*: Causes schistosomiasis.
These pathogens can diversify significantly in their mechanisms of infecting and harming their hosts, but all lead to various forms of disease.
Definition of pathogens
State six types of pathogens and give three examples
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