A pathogen is a biological agent, such as a virus, bacterium, fungus, protozoan, or parasite, that causes disease in its host organism. Pathogens have the capability to invade host tissues, replicate, and disrupt normal physiological functions, leading to the development of an infection or disease.
Pathogens can infect various organisms, including humans, animals, plants, and even other microorganisms. They can spread through various means, such as direct contact with an infected individual, ingestion of contaminated food or water, inhalation of airborne particles, or through vectors like mosquitoes or ticks.
The human body has various defense mechanisms, such as the immune system, to combat pathogens. However, some pathogens have evolved mechanisms to evade or suppress these defenses, leading to persistent infections or more severe diseases.
Understanding pathogens and how they interact with their hosts is crucial for developing strategies to prevent, diagnose, and treat infectious diseases. This knowledge also plays a significant role in public health efforts aimed at controlling the spread of infections and minimizing their impact on populations.