What is the Chain of Infection?
The Chain of Infection is a model used by healthcare professionals to describe how infectious germs are spread and transmitted. There are six links to the chain of infection: pathogen, reservoir, portal of exit, mode of transmission, portal of entry, and host. Some places may use different terms, but they all share the same meaning. The chain of infection is important in preventing the spread of disease because it highlights the points at which the chain can be broken. This post aims to break down each link and its role in the Chain of Infection.
Pathogen
A pathogen is a biological agent that causes disease. There are four common types of pathogens: bacteria, viruses, fungi, and protozoa. Each type has unique characteristics and reacts differently in your body. Some pathogens spread more easily than others, infecting larger numbers of people. This is due to factors like how long they can survive outside the body and their reproductive rate. Pathogens that are considered to be highly infectious include: chickenpox, COVID-19, and Tuberculosis.
Reservoir
Once the pathogen is established, it needs a place to live. The reservoir of the Chain of Infection is where the pathogen resides and multiplies. A reservoir can include people, animals, medical equipment, food, and many other things. To kill pathogens in the reservoir, you should make sure to sanitize surfaces, practice good hygiene, and isolate if infected.
Portal of Exit
Once the germ has an established home, it needs to leave so it can spread to others. The portal of exit is how a pathogen leaves a reservoir. It can be through blood, respiratory secretions, and other bodily fluids. If you are sick, it is important to be cautious of open wounds, coughing, and sneezing. To stop the spread of infection, personal hygiene is critical. Sneeze and cough into your arms to stop the pathogens from transmitting to others.
Mode of Transmission
The mode of transmission is how the pathogen transfers from the reservoir to the host. There are a few different modes of transmission.
The most common type of transmission is through contact. It can be direct (touching someone who is sick) or indirect (touching a contaminated object). To avoid this transmission, avoid individuals who are sick and disinfect surfaces.
The next type is airborne transmission. It happens when pathogens are carried by particles in the air. If someone coughs or sneezes, the pathogens can linger in the air. To avoid this, cover your coughs and sneezes!
Another common type of transmission is vector-borne. Vector-borne transmission is when pathogens are transferred through living carriers. The most common vectors are ticks, mosquitoes, or rodents. It is important to be cautious around insects and other animals that could be carrying a disease.
Portal of Entry
To infect others, the pathogen needs to enter a new host. The portal of entry is how the pathogen enters the body. A pathogen can enter the body in various ways. Inhalation is when the pathogen enters the body through the respiratory tract. Pathogens also enter the body through absorption into the skin or mucous membranes. Inoculation is the penetration of a contaminated object into the skin. And lastly, ingestion, which is when a pathogen enters your body through the digestive tract. To prevent an infection from entering your body, you can use proper hygiene, wear personal protective equipment, follow food sanitation rules, and properly clean any wounds you get.
Host
Lastly, the host is the person the pathogen is entering. Some individuals are more susceptible to germs than others. Individuals who are very young or old are more susceptible because of their weak immune systems. Certain medical conditions and medications can also weaken your immune system. By leading a healthy lifestyle, exercising, eating healthy, and not drinking or smoking, you can decrease your susceptibility to infection.
Example
Let’s run through an example of how a germ can travel to others using the chain of infection.
Timmy is going to the doctor because he has a fungal infection on his foot and needs anti-fungal medication. He walks into the office and takes off his shoes so the doctor can examine him. He puts his bare foot on the table. After his appointment, he leaves the office. The workers at the clinic are so busy that they forget to sanitize the table before the next patient comes in. The next patient, Sarah, needed to get her height and weight checked, so she also needed to take off her shoes. When she goes to put her shoes back on, she puts her feet on the table to make it easier. Unfortunately for her, Sarah got a fungal infection on her feet because of this mistake.
In this scenario, the pathogen is a fungus. Timmy is the reservoir. Timmy’s foot comes into contact with the table, and the pathogen can exit Timmy’s body onto the table. This is a portal of exit. The contaminated table is the mode of transmission because the pathogen indirectly spread the disease to another patient. When Sarah puts her bare feet on the table, the pathogen enters her body, making this the portal of entry. Lastly, Sarah is the new host because the pathogen established itself on her.
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