Chain of Infection
The chain of infection consists of six steps; pathogen, reservoir, portal of exit, method of transmission, portal of entry, and the host. This looks difficult at first. However, it is easy because the portals of entry and exit are sometimes the same. The reservoir and the host can also be the same.
First there has to be a pathogen or some germ that makes a person sick. If there were no pathogens or germs, nobody would ever get sick. It would be good if people never got sick. Unfortunately, there are germs. Germs get in and out of our bodies. Remember, germs and pathogens are the same. Germs and pathogens make a person sick.
The reservoir is the place where the pathogens get bigger. A reservoir can be food, water, an animal, or a person. A reservoir is any place that the germs can get the things they need to survive. But, we don't want pathogens living in our bodies. Pathogens cause diseases that make us sick. We want to stop them from growing. Remember the different types of pathogens; foodborne, waterborne, airborne, and bloodborne. The reservoir is where the pathogen is living.
Pathogens need to be able to get in and out of the places they grow. Airborne pathogens can exit the body through the mouth and nose. Bloodborne pathogens can get out of the body through a cut or opening in the skin. Any place a pathogen can get out of a body is a portal of exit. Think of the portal of exit and the portal entrance as a doorway for germs to get inside the body and outside.
There are two ways pathogens can spread. There is indirect transmission and direct transmission. Transmission and exposure are similar. A person could say he was exposed to a pathogen through indirect exposure. Or, he was exposed to a pathogen through direct exposure. Let's look at both.
1. Direct Transmission
Direct transmission means a person was exposed to a pathogen by touching another person; hugging, kissing, handshakes, and cuddling are all ways pathogens can be directly transmitted.
2. Indirect Transmission
Indirect transmission means that a person is exposed to a pathogen indirectly. To be exposed to germs indirectly means that germs have gotten onto another object like a door handle, coffee cup, pen, pencil, shared , etc.
If someone sneezes or coughs, touches an object, and another person touches the object the person got germs on, this is indirect transmission because two people were not touching.
The portal of entry is the place where germs get into the body. This could be the mouth, nose, eyes, or other body parts with openings. It could also be when a person gets a cut and there is an opening in the skin.
Host
The host is the place, person, or animal where the germs grow. The host is sometimes the same as the reservoir because that is where the pathogen can grow and spread causing the host to get sick.
