11: EPIDEMIC
- Page ID
- 157071
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- Record and organize experimental data related to simulated disease transmission using observation and peer interaction tracking.
- Describe how chain-of-contact tracing contributes to disease tracking.
BACKGROUND
An epidemic occurs when the number of individuals affected by a specific infectious disease rises significantly above what is normally expected within a particular population or region. The study of epidemics, known as epidemiology, focuses on identifying the causes of disease outbreaks, understanding how they spread, and developing strategies to control them. Much of this work involves careful investigation, pattern recognition, and tracing the origin of the pathogen—similar to solving a mystery.
When the source of an outbreak can be identified, public health officials are better equipped to contain the spread and prevent future infections. However, when the origin remains unknown, the risk of repeated outbreaks increases.
In today’s lab, you will participate in a simulated epidemic that models how a disease can spread within a population. To conduct this simulation, the bacterium Serratia marcescens will be used. S. marcescens a gram-negative organism commonly used in microbiology labs. It is generally harmless to healthy individuals and easily recognized due to its production of a natural red pigment called prodigiosin. This pigment allows you to visually track the transmission of the “infection” during the exercise.
In real outbreaks, infections often spread in a stepwise fashion through chains of contact. This lab will replicate that process. By recording your interactions and analyzing patterns of spread, the class will work together to identify the original source of the infection.
It is important that you follow all instructions carefully and label correctly, as the success of this simulation depends on the accuracy of your data. During the next lab session, the information on the inoculated plates will be used to determine which student was the initial source of the epidemic.
MATERIALS (Per Student)
1 plastic glove
1 candy in numbered dish (one is contaminated with Serratia marcescens)
1 tube of sterile water|
1 sterile cotton swab
1 petri dish of nutrient agar
METHODS/PROCEDURES
1. Label the bottom of your petri dish with five sections labeled 1 through 5. Numbers should be large and easy to read from the top of the dish. In the
center, write your last name, today’s date, and the candy ID number.
2. When directed by your instructor, put a glove on your non dominant hand (the hand you do not write with). With your ungloved right hand, open the
plastic bag containing the candy. Use your gloved hand to pick up the candy and smear it all over the palm of the glove. Do not touch anything else
with the candy.
3. When told to do so, shake hands (glove to glove only) with one person in the lab. After shaking hands, exchange ID numbers. This person is your first
contact.
4. After the handshake, swab the surface of your gloved palm using a sterile swab. Rub the swab across section 1 of your petri dish. Return the swab to
the sterile water tube. Record the ID number of your first contact in section 1.
5. When instructed, shake hands with a new person in the room (do not shake hands with the same person more than once). After the handshake, swab
your gloved palm again with the same swab and streak section 2 of your plate. Place the swab back into the water tube. Record the new contact’s ID
number in section 2.
6. Repeat the handshaking and swabbing process until you have completed five rounds. Remember to always shake hands with someone new. Each time,
use the same swab and streak the appropriate numbered section of your plate.
The following is to be completed during lab then turned in on Canvas as a PDF
*If you are using an iPad or tablet you will need to take screen shots of your competed work, save the screenshots as one PDF then submit them on Canvas by the due date designated on Canvas.
*You can also print out the entire exercise to bring to lab with you. If you choose to complete the lab on paper, take pictures of the completed results and conclusions sections only, save them as one PDF, then submit to Canvas by the due date designated on Canvas.
EPIDEMIC
NAME ______________________
EXPECTATIONS
How many students do you think will be infected by the fifth round of contact? Explain your reasoning.
RESULTS
Draw the growth on your test plate after incubation. Be sure to note the color of growth.
CONCLUSIONS
1. Why was red colony growth the only type recorded during this experiment?
2. How would using white candy instead of red have compromised the results of this simulation?
3. Public health professionals often face challenges when investigating real epidemics that were not present in our classroom simulation. Describe three factors that make tracking a real-world outbreak more difficult.
4. This simulation modeled disease spread through direct contact, allowing us to document each interaction. Why would an airborne epidemic be more difficult to trace using the same method?