When a microbe harms a person after entering their body, an infection happens. The microorganism lives off of that person’s body and reproduces and colonises there. These pathogenic tiny organisms are contagious and reproduce swiftly. Pathogen examples include: bacterias, viruses, fungi. They differ in a number of ways, such as size, function, genetic makeup, and effects on the body. For instance, compared to bacteria, viruses are smaller. While bacteria can exist without a host, they infiltrate a host and take over cells. 

The cause of the infection will affect the course of treatment. They can spread through a variety of channels, such as skin-to-skin contact and body fluid transfer, contact with excrement, consuming tainted food or water, inhaling airborne particles or droplets, or contacting a surface that has been handled by a person who is carrying the disease. Indirect touch can potentially spread disease-causing organisms. An inanimate object, like a tabletop, doorknob, or faucet handle, can harbour a lot of germs.