The main cause of infection is the entry and multiplication of pathogenic microbes, such as viruses, bacteria, fungi, or parasites, within the body.
These microbes, once inside the body, can disrupt normal cellular processes, leading to damage and the manifestation of disease symptoms. The infection process typically involves the following steps:
- Entry: Microbes enter the body through various routes, including:
- Skin (cuts, wounds)
- Respiratory tract (inhalation)
- Digestive tract (ingestion)
- Urogenital tract
- Direct inoculation (e.g., insect bites, injections)
- Attachment: After entry, microbes attach to specific cells or tissues within the body.
- Multiplication: The microbes then begin to multiply, increasing their numbers within the host.
- Evasion of Host Defenses: Pathogens employ various mechanisms to evade the host's immune system, allowing them to persist and spread.
- Damage: As the microbes multiply and spread, they cause damage to the host's cells and tissues, leading to the signs and symptoms of infection. This damage can result from:
- Direct destruction of cells by the microbe.
- Release of toxins that damage tissues.
- Activation of the host's immune system, which can lead to inflammation and collateral damage.
In summary, infection arises from the successful invasion and proliferation of pathogenic microbes within the body, ultimately causing harm and triggering disease.
