WHAT IS AN INFECTION?

An infection is a disease caused by microorganisms that invade tissue.

To understand, we need to get some important terms out of the way. A microorganism is a small, living organism that is not visible to the naked eye. A pathogen, which is another term for causative agent, is a microorganism that has the potential to cause a disease. There are different types of pathogens, including fungi, bacteria, viruses, protozoans, and prions.

Now, we need to get some things clear. A virus is even smaller than bacteria, and needs a living host, such as animals, humans, or plants to multiply. This connects to the chain of infection. A chain of infection consists of six things. One of those is a causative agent, which is a pathogen (such as a bacterium or virus) that can cause disease. There is the reservoir which is the place where a causative agent can live. There is a portal of exit which is the way for a causative agent to escape from the reservoir. There is also a portal of entry which is the way for a causative agent to enter a new host. Lastly, the mode of transmission is the way that a causative agent can be transmitted to a susceptible host. That susceptible host is an individual who can contract a disease.

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