What am I supposed to do?

Read the narrative carefully, and then examine the dataset in Excel FILE as ‘ENH 122 OHS DATA’. The data are posted as an excel spreadsheet. The variables are defined in the ‘Data dictionary’ within the third sheet of the Excel file.

Your mission is to examine the association between the illness and the MANY possible exposures, so as to provide, as far as you can, the answers to the questions:

  1. What was the agent responsible for the illness?
  2. What was the vehicle or activity associated with the illness? 
  3. Was there an environmental component to the exposure? 

To answer these questions, you need to search for patterns. WHO was most at risk, and WHAT activities and exposures led to the illness? To make your conclusions, use ALL the evidence at hand, and the results from your various analyses and calculations. We are not interested in your ‘feelings’ and ‘hunches’, just the evidence. A helpful list of potential agents and their environmental sources has been provided. Eliminate one at a time until you can eliminate no further.

Follow the 14-point investigation and USE the numbers (1-14) in labelling your responses. You do not need to write out the question, just use the question number for your response.

This is to be a professional report, not a hastily prepared student assignment. Please pay attention to the English language (spelling, grammar, syntax, punctuation), and the layout. Please limit your submission to 5 pages (11 pt. font, single spaced). The 5 pages do not include the cover page or the references.

Where you are citing or using ideas, concepts, and information that is not your own, proper attribution of the source is required. Use APA style on citations and references.

Make sure the front page contains the information shown below.
Cover page to show:

(Your name(s) – – and student number(s))

To: Dr. ……

Special note about plagiarism:
I expect the work to be your own. We routinely check similarities with other submissions manually and via Turnitin. Often, several students have been charged with academic misconduct and a disciplinary notice (DN) has been added to the student’s academic records. This has been due to unexplained similarity in text or graphics with other students. If you wish to discuss the project with others, make sure that ALL the work submitted is your own.

This is not a difficult assignment, but it is a valuable first exercise in field epidemiological investigation.


You are the staff OH&S specialist at a large diamond mine in a remote region of Australia. On occasion, high preforming workers are offered the choice to take the day away from their usual work and instead spend the day watching for forest fires in the very comfortable, high tech watchtower. During early January, the company medical centre reports several cases of nausea, vomiting and low grade fever in workers who had all been given this duty. Many have been hospitalized. It is uncertain if the cases are related to this activity or if it may be a more widespread problem due to chemical exposure. Human and environmental samples have been taken but they have to be flown to the laboratory for analysis and will not be available for about a week. As all the patients are workers for the company, and the infections occurred while on the job, you (as the OH&S specialist with some knowledge of epidemiology) are working alongside the company’s medical assistants to investigate the problem. Reports for the entire group of workers for the previous several months show roughly 1-2 cases of this type of pneumonia every month.


  1. Plot the time of onset for each person (the “epidemic” curve), using one-day intervals for each day of the month. The histogram should be clearly-labelled (title, y and x axis) and easily read, and should clearly show the time of onset.
  2. Next, plot the “elapsed time” curve which shows a time of ‘zero’ for each person’s tower shift, and the distribution of marks for each person following the shift (Use the same 1-day intervals). This has the effect of accumulating everyone together relative to their own tower shift day as if it were the same moment.
  3. What does this tell you about the range of the incubation period as well as the median incubation period?
  4. Is there evidence of propagation in this outbreak? Why or why not?
  5. Does this constitute an “epidemic”? Why or why not?


  1. Some workers who took a watchtower shift regularly work in multiple locations. Table 1 shows the work locations of each watchtower shift employee. Is there an association between exposure to any particular work location and the illness? Interpret your results [2×2 tables needed with odds ratios] 
  2. You have asked for the incidence of reports of this type of pneumonia in the general worker community who did not have a tower shift during January but the cases are very few, and none directly traceable to the tower workers. What statement can you make about clustering in ‘place’? PERSON: 
  3. Is there a relationship between gender and illness among the tower workers during January? Interpret your results [2×2 analysis needed with odds ratios]
  4. Is there a relationship between age group (i.e. 16-20, 21-25, etc.) and illness in the volunteers during January? Interpret your results [2xN analysis needed]
  5. Is there a relationship between the occupation and the illness? Interpret your results [2xN analysis needed]
  6. What was the overall attack (incidence) rate among the patients during January? 
  7. Make a symptom profile table showing the percentage of the ill persons who demonstrate the symptoms. Describe the symptom profile.

NOTE: SYMPTOM DATA IS NOT DISPLAYED IN EXCEL FILE: The symptoms are limited to pneumonia (=all patients), with cough (=7 patients), fever (=4 patients), and abdominal pain (=3 patients).

  1. Given ALL the evidence you have thus far, and after consulting information sources, try to eliminate as many as possible of the agents on the following list. 
    • Mononucleosis
    • Diphtheria
    • Legionellosis
    • Norovirus
    • Staphylococcus 
    • Streptococcus Group A

Where you can eliminate any of these agents, explain specifically why it is NOT likely to be that agent. What are you left with?

  1. Write two paragraphs (not point form!) summarizing the outbreak for a public health professional journal. This should contain all the important information, evidence, results, and recommendations from your investigation. Be Clear, Concise, and Accurate. 
    • Are you able to identify a specific exposure? Which? Explain why. Are you able to identify a specific agent? Which? Why? Your conclusion should be based on the reasons for eliminating the others. For this you will need to read the characteristics of the suggested agents in the CCD Manual. Remember you can only eliminate aetiologies when you have appropriate evidence. Otherwise they are still candidates.