The Chain of Infection

Feb 28, 2018 · 5 min read


People get sick all the time and most people think that getting sick is inevitable. However, there are certain measures people can take to prevent getting sick or spreading their sickness to others. We will learn what steps we can follow to prevent the spread of germs and disease by first understanding the chain of infection. The way the chain of infection works should be known by everyone in order to protect ourselves and those around us. Taking proper precautions to keep ourselves and our things clean can help break the chain of infection and stop a disease right in its tracks.

What is the chain of infection?

The chain of infection is a cycle, just like the water cycle, that shows the various steps a disease must take in order to infect someone. Not only does it show the steps a disease must follow but also steps people can take to break the chain of infection and stop a disease. The cycle includes six steps a disease must take before it can infect someone. These steps are

· Infectious germ

· Reservoir

· Portal of exit

· Mode of transmission

· Portal of entry

· Susceptible host

Step 1: Infectious Germ

The first step is less of a step and more of a must. In order for there to be a chain of infection there must first be an infectious germ. This germ could be bacteria, a virus, fungi, or a parasite. This first step can also start with a human that is already infected. It is easiest to break the chain of infection in the first step if you are the one infected. All you need to do is go to your doctor and get a diagnosis and treatment. Just like that you have broken the chain.

Step 2: The Reservoir

The reservoir of an infectious germ is a place where the germ can typically be found living, growing, and multiplying. Reservoirs include humans, animals, and the environment. Many common infectious diseases have strictly human reservoirs such as strep throat and sexually transmitted diseases. Carriers of infectious diseases can often be unaware that they are sick or contagious in the first place which leads to the carrier not taking the correct precautions to prevent further spread. To break the chain at this step it is important to clean and disinfect common areas such as your home, work area, or even your car. Pest control can also help break the chain because pests like mice and mosquitos carry many infectious and even deadly diseases.

Step 3: Portal of Exit

Portal of exit simply means a way for the infectious germs to leave your body. Germs can leave the body in many different ways. Most diseases can be spread by mouth by coughing or sneezing. However, infectious germs can also be found leaving the body through urine, feces, blood, other bodily fluids, and even from a pregnant mother to her child through the placenta. To break the chain at this step it is important to always use good hand hygiene, wear personal protective equipment such as gloves or a mask, correct waste disposal, and good respiratory etiquette which means cover your mouth when you sneeze or cough.

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Step 4: Mode of Transmission

Mode of transmission refers to the way that germs are spread from one place to another. These transmissions can either be direct or indirect. Direct transmission can come from direct contact with an infectious germ or from droplet spread which means sneezing or coughing and having droplets of fluid containing the disease land on or inside someone. Indirect transmissions can come from airborne, vehicle-borne, or vector-borne. Airborne transmission happens from the infectious germ being present in the air you are breathing. Vehicle-borne transmissions happen from using contaminated materials such as a fork or piece of clothing. Lastly, vector-borne transmissions happen when an insect like a mosquito bites you and infects you. To break the chain at this step it is important to use good hand hygiene, understand food safety, and clean common areas.

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Step 5: Portal of Entry

The portal of entry refers to the way that an infectious germ enters the body of a healthy person. Most of the time, infectious germs use the same portal to enter a new person that it used to leave the last person like the flu virus. The ways of entry include mouth, nose, skin such as an open wound, and blood perhaps from using a contaminated needle. To break the chain at this point it is important to have good hand hygiene, use personal protective equipment, maintain good personal hygiene, and most importantly get first aid for open wounds.

Step 6: Susceptible Host

A susceptible host is anyone that is not immune to whatever the disease may be, especially those receiving healthcare. Susceptible hosts rely on everyone and themselves to use good hygiene and proper preventative measures to ensure their health. To break the chain at this step it is important to get immunizations, treat underlying diseases, and follow the steps to break the chain at all other steps.


People get sick all the time but if we work together to maintain a healthy and clean community we can greatly reduce the risk of infection. The most important thing you can learn from this is good hygiene. As humans we us our hands for everything so you can’t avoid getting your hands dirty, just make sure to wash them. When you keep up with good hygiene it benefits everyone around you. So next time you cover your mouth when you cough or sneeze, think of it as a good deed.

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It begins with the infectious agent

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