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Let's review some key ideas of epidemics in a human community. Consider the following questions yourself before unfolding the answers.
Let's review some key ideas of epidemics in a human community. Consider the following questions yourself before unfolding the answers.
What is an epidemic from a systems perspective?
What is an epidemic from a systems perspective?
An epidemic is a rapid increase in the number of cases of an infectious disease within a population. It is an emergent phenomenon caused by the simultaneous and continuous interactions between humans and the disease pathogen, as well as among humans themselves. The characteristics of both the pathogen and humans, along with how they interact, determine whether an epidemic occurs and how it progresses (e.g., rapidly or slowly).
How are decentralization and stochasticity reflected in an epidemic?
How are decentralization and stochasticity reflected in an epidemic?
The interactions among humans and between humans and pathogens are carried out by individual humans or viruses, rather than being controlled by a central force or unit. Therefore, all interactions are decentralized. Even though governments may implement lockdowns or travel restrictions, these policies are still carried out by each individual.
Stochasticity exists in many parts of the system where an epidemic occurs, leading to uncertainties. Humans vary in their likelihood of getting infected, their chances of recovery, and their risk of death. Variations also exist in whether and how people comply with government policies. Viruses may mutate randomly, generating new strains. Therefore, different epidemic outcomes may emerge even with the same initial conditions. While they may fall within a certain outcome range, they will not be identical.
How do different factors influence an epidemic?
How do different factors influence an epidemic?
An epidemic can be influenced by many factors that originate from the humans or pathogens in the system. Given they interact with one another over time, a small difference in the inputs may accumulate into large differences in the outputs, as revealed in the data you collected in the computer model. The graphs below provide more information when we consider two factors together [16].
How can we effectively mitigate an epidemic?
How can we effectively mitigate an epidemic?
Given that many factors can affect the maximum number of daily cases, there are many ways to mitigate infectious disease outbreaks. For example, we can maintain a less crowded population, use personal protective equipment (PPE) to lower the transmission rate, limit travel to reduce mobility, and vaccinate the population. However, many of these strategies cannot be implemented in the long term. Among the available options, vaccination is the most effective approach because it can quickly protect the largest number of people with minimal disruption to our daily lives.
It is not possible to vaccinate everyone for various reasons. Therefore, public health experts need to estimate the herd immunity threshold, which is the percentage of the population that needs to be immune (either through vaccination or previous infection) to stop the spread of an infectious disease and protect those who are not immune. The herd immunity threshold can vary depending on the disease and the specific conditions of the community. The graph below shows the different herd immunity thresholds for different transmission rates and population densities [16].
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