Common Diseases in Human Beings

The disease can be defined as a disorder or malfunction of the mind or body. It involves morphological, physiological, and psychological disturbances that may be due to environmental factors, pathogens, genetic anomalies or lifestyle changes.

• A wide range of organisms belonging to bacteria, viruses, fungi, protozoans, helminths, etc. could cause diseases in human beings. Such disease-causing organisms are called pathogens. 
• Pathogens are transmitted through air, water, food, physical contact, and vectors.
• A parasite is an organism that lives on or in a host organism and derives its food from its host. A pathogen is a bacterium, virus, or other microorganism that can cause disease.
• Most parasites are therefore pathogens, as they cause harm to the host by living inside or outside the host's body.
• Pathogens have to adapt to life within the environment of the host. For example, the pathogens that enter the gut must know a way of surviving in the stomach at low pH and resisting the various digestive enzymes.
• The pathogens can enter our bodies by various means, multiply and interfere with normal vital activities, resulting in morphological and functional damage.