Microorganisms cause diseases in humans by infecting the body and damaging cells, which leads to the appearance of illness signs and symptoms.
Here's a more detailed breakdown:
Microorganisms, including bacteria, viruses, fungi, and parasites, can cause disease when they:
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Enter the body: Microbes can enter through various routes, including:
- Inhalation: Breathing in airborne droplets containing pathogens (e.g., influenza virus).
- Ingestion: Consuming contaminated food or water (e.g., Salmonella bacteria).
- Direct contact: Physical contact with an infected person or contaminated surface (e.g., Staphylococcus aureus).
- Wounds: Pathogens entering through broken skin (e.g., Clostridium tetani causing tetanus).
- Vectors: Transmission by insects or animals (e.g., Plasmodium parasites causing malaria through mosquito bites).
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Multiply: Once inside, microorganisms reproduce and increase their numbers.
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Damage Cells and Tissues: Microbes employ various mechanisms to harm the body:
- Direct Cell Damage: Some microorganisms directly destroy cells as they replicate, such as viruses hijacking cellular machinery for their own reproduction, ultimately killing the cell.
- Toxin Production: Bacteria can release toxins that damage tissues and disrupt normal bodily functions (e.g., Clostridium botulinum producing botulinum toxin causing botulism).
- Immune Response: The body's immune system, while designed to protect, can sometimes contribute to disease symptoms. Excessive inflammation, triggered by the infection, can damage healthy tissues (e.g., sepsis).
- Biofilm Formation: Some bacteria form biofilms, communities of microorganisms attached to a surface, which can be resistant to antibiotics and the immune system, leading to chronic infections.
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Cause Signs and Symptoms: The damage to cells and tissues results in the signs and symptoms of disease, which can vary depending on the type of microorganism and the affected body system.
In summary, microorganisms initiate disease by entering the body, multiplying, and damaging cells through direct destruction, toxin production, or triggering a harmful immune response. This damage then manifests as the signs and symptoms of illness.
