When referring to the epidemiological triad, the interactions of the host, agent, and environment correlate with the spread of infectious diseases (Lesson 1: Introduction to Epidemiology, 2012). The epidemiological triad is designed to be shaped like a teeter totter with the environment being the base, the host being on one side and the agent being on the other (1.2 – Epidemiologic Triad, n.d.). When the teeter totter is balanced it is known as the equilibrium state, this state signifies that everything is healthy. In a scenario where there is an infectious disease, the teeter totter would be weighted towards one side. The goal of an epidemiologist is to decipher the connection between any of these three main factors. (1.2-Epidemiologic Triad, n.d.)

Imbalance towards the Agent

When looking at the epidemiological teeter totter, there are moments when there is an imbalance that causes many different scenarios. If the imbalance is towards the agent it is considered as the agent having more of an ability to cause a disease on man (The Epidemiologic Triad, n.d.). This can be shown by the zika virus, as this disease has caused a pandemic and is still showing different side effects that have never been seen. The zika virus is transmitted by mosquito bites and causes fever, rashes, headaches, joint pain, red eyes, and muscle pain which typically lasts for several days to a week. However, if transmitted to a pregnant women, the child will have birth defects that will affect them for the rest of their lives (Zika Virus, 2017). In this situation, the mosquitos are the agents carrying the zika virus and infecting the host, humans. The mosquitos have also more control of passing the disease because of their size and how many reproduce. Also, there is no ability to tell the difference between a regular mosquito bite with no zika and one that has zika. This allows the host to transmit the disease via sex with other potential hosts without even knowing. Eventually, this expanded the area the disease infected because of the agent’s ability to transmit the disease to the host.

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Imbalance Towards the Host

Another outcome that is shown in the imbalance of the epidemiological teeter totter is towards the host. This imbalance explains that the amount of ways a person is susceptible to a disease increased (The Epidemiologic Triad, n.d.) A good example of this can be shown by the H1N1 flu virus. The flu virus is transmitted from person to person through contact with others who have the flu or possibly through surfaces that people with the flu have touched in the past. Every year, people get infected with the flu virus even if they have had it in the past or have taken flu vaccines. This is because the H1N1 flu virus is an RNA virus, which means that it mutates and changes every so often (Influenza (Flu), 2017). This forces doctors to change the flu vaccine every year to try and decrease our susceptibility. Unfortunately, there’s a possibility that the vaccine may not work and can still cause you to contract the virus. This, ultimately, leaves people vulnerable to the disease whether they are vaccinated or not. This shows how a host’s susceptibility to a disease may increase because of the agent and environment they’re in.

Imbalance Towards the Environment

The environment also plays a key role in how the agent and host are affected by a disease. The environment plays a role in where the disease is most likely to spread and where it is currently located. With the use of previously explained diseases, the zika virus is only found in places with a hot climate such as South America, Africa, and India (Zika Virus, 2017). Although the flu is a disease that is common worldwide, it is typically transmitted in the colder months of the year. This shows epidemiologists that more prevention should be placed on these areas when the climate correlates with the rate of susceptibility to the host. In certain times of the year, in specific environments, the host may not have a high susceptibility to certain diseases, but may be susceptible to others. Just like the host and the agent, the environment has direct correlation to the other factors when spreading a disease.