3. Consider the following data (table 1) reported during an outbreak of bubonic plague in Eyam, England. It can be described by the SIR model without demographics. (2) \frac{dS}{dt} = -\beta SI, \frac{dI}{dt} = \beta SI - \gamma I, \frac{dR}{dt} = \gamma I, where $S(0) = 254$ and $I(0) = 7$. (a) For $\beta = 0.0134$ and $\gamma = 2.19$ plot the model and the data. TABLE 1. Bubonic plague from year 1666. Date (1666) Susceptibles Infectives July 3/4 235 14.5 July 19 201 22 August 3/4 153.5 29 August 19 121 21 September 3/4 108 8 September 19 97 8 October 20 83 0 (b) Explain why this is not a good model by researching the way bubonic plague is transmitted. Write a more realistic model for this outbreak and plot its solutions.
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In 1666 the village of Eyam, located in England, experienced an outbreak of the Great Plague. Out of 261 people in the community, only 83 survived. The table shows a function $f$ that computes the number of people who had not (yet) been infected after $x$ days. $$\begin{array}{|c|r|r|r|r|}\hline x & 0 & 15 & 30 & 45 \\\hline f(x) & 254 & 240 & 204 & 150 \\\hline\end{array}$$ $$\begin{array}{|c|c|c|c|c|}\hline x & 60 & 75 & 90 & 125 \\\hline f(x) & 125 & 103 & 97 & 83\\\hline\end{array}$$ (a) Use a table to represent a function $g$ that computes the number of people in Eyam who were infected after $x$ days. (b) Write an equation that shows the relationship between $f(x)$ and $g(x)$ (c) Use graphing to decide which equation represents $g(x)$ better $y_{1}=\frac{171}{1+18.6 e^{-0.0747 x}}$ or $y_{2}=18.3(1.024)^{x}$ (d) Use your results from parts (b) and (c) to find a formula for $f(x)$
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Identity and discuss a bacterial disease that caused a historically important plague or epidemic. What is the modern distribution of this disease? a. Bubonic plague caused by Yersinia pestis was a pandemic that occurred in the 14th century. In modern times, there are only about 100 cases of bubonic plague each year. The bacterium responds well to modern antibiotics. b. Bubonic plague caused by Yersinia enterocolitica was a pandemic that occurred in the 14 th century. In modern times, there are about $1,000$ to $3,000$ cases of bubonic plague each year. The bacterium responic plague modern antibiotics. c. Pneumonic plague caused by Yersinia pestis was a pandemic that occurred in the 14 th century. In modern times, there are about $1,000$ to $3,000$ cases of pneumonic plague each year. The bacterium responds well to modern antibiotics. d. Bubonic plague caused by Yersinia pestis was a pandemic that occurred in the 14th century. In modern times, there are about $1,000$ to $3,000$ cases of bubonic plague each year. The bacterium responds well to modern antibiotics.
Differential equations can be used to model disease epidemics. In the next set of problems, we examine the change of size of two sub-populations of people living in a city: individuals who are infected and individuals who are susceptible to infection. $S$ represents the size of the susceptible population, and $I$ represents the size of the infected population. We assume that if a susceptible person interacts with an infected person, there is a probability $c$ that the susceptible person will become infected. Each infected person recovers from the infection at a rate $r$ and becomes susceptible again. We consider the case of influenza, where we assume that no one dies from the disease, so we assume that the total population size of the two sub-populations is a constant number, $N$. The differential equations that model these population sizes are $$S^{\prime}=r I-c S I \quad \text { and} $$ $$I^{\prime}=c S I-r I.$$ Here $c$ represents the contact rate and $r$ is the recovery rate. Draw the directional field
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