Hot tub folliculitis among hotel guests after a youth swim meet, investigated from line list to control measures in a composite MN505 Unit 4 memo. Searches like "mn 505 unit 4 assignment example", "mn505 unit 4 sample" and "mn505 unit 4 example" land here.
Outbreak Investigation Memo: Rash Illness Among Guests of a Hotel Hosting a Youth Swim Meet
[Student Name]
Purdue University Global
MN505: Epidemiology and Health Promotion
Unit 4 Assignment
[Instructor Name]
[Date]
The hotel, guests and figures are composites written as a model document. No real outbreak, business or person is described.
Memo Header and Bottom Line
To: County Health Officer. From: Epidemiology Nurse, Communicable Disease Program. Date: March 18, 2026. Subject: Rash illness among guests of a downtown hotel, March 7 to 9, 2026.
Bottom line: 25 guests developed an itchy red rash after a youth swim meet weekend. Illness was strongly associated with using the hotel hot tub (23 of 38 users ill, 60.5 percent) and not with the pool alone. The hot tub had low free chlorine and grew Pseudomonas aeruginosa. The findings are consistent with hot tub folliculitis caused by Pseudomonas aeruginosa, and the hot tub has been closed until it is cleaned, disinfected and retested.
1. Preparation and Verification of the Diagnosis
On March 10, an urgent care clinician reported four children from the same swim team with a rash of itchy red papules and pustules on the trunk, buttocks and thighs. Photographs showed a follicular pattern, and a culture of one pustule grew Pseudomonas aeruginosa. The diagnosis was confirmed before any case count began, following the sequence in the CDC field guidance (Rasmussen & Goodman, 2019).
2. Establishing the Existence of an Outbreak
The expected number of rash illnesses linked to one hotel over one weekend is zero, so four reported cases from one group established an outbreak.
3. Case Definition
A case was defined as a new rash of papules or pustules, with or without itching, beginning within 72 hours of arrival, in a person who stayed at or visited the hotel from March 7 to 9, 2026. A culture was not required, because most people with this rash are not cultured.
4. Case Finding
Cases were found through the swim meet's registration list, which named every athlete, coach and accompanying family member staying at the hotel. All 64 guests on the list were contacted by phone or email with a standard questionnaire, and 64 responded. Using the registration list, rather than only people who called, meant that guests who used the hot tub and stayed well were counted too.
5. Descriptive Epidemiology
Person: 25 cases, ages 9 to 46, with a median age of 13; 19 were athletes. Place: all cases stayed at or visited the hotel. Time: onset ranged from 8 to 48 hours after first hot tub use, with most onsets between 12 and 30 hours. The onset histogram in six-hour bins shows a single peak consistent with exposure over one weekend. Symptoms: rash in 25, itching in 21, ear pain in 4, mild fever in 2. No one was hospitalized.
6. Hypothesis and Analytic Comparison
The pattern of onset and the age of cases pointed to a recreational water exposure. Attack rates by exposure: hot tub users, 23 of 38 ill (60.5 percent); pool only, 2 of 19 ill (10.5 percent); neither, 0 of 7 ill. Comparing those who used the hot tub with those who did not (2 of 26 ill, 7.7 percent), the relative risk was 7.9 (95 percent confidence interval 2.0 to 30.5), calculated as described in standard field methods (Centers for Disease Control and Prevention, 2012). The two ill guests in the pool-only group both reported sitting on the hot tub's edge with their legs in the water, which may explain their illness.
7. Environmental Findings
On March 11, an environmental health specialist inspected the pool and hot tub. The hot tub's free chlorine was 0.4 parts per million, below the state minimum of 3.0 for spas, and the heater was set at 104 degrees Fahrenheit. The pool's free chlorine was within range. Samples from the hot tub filter grew Pseudomonas aeruginosa. Warm water and low disinfectant levels allow Pseudomonas to multiply, and outbreaks of folliculitis after whirlpool use have been described repeatedly (Ratnam et al., 1986).
8. Control Measures, Communication and Surveillance
The hot tub was closed on March 11 and will remain closed until it has been drained, cleaned, disinfected and shown to have adequate free chlorine on repeat testing. The hotel has agreed to check free chlorine in the spa every four hours while it is open. A letter was sent to all 64 guests explaining that the rash usually resolves on its own within one to two weeks and advising them to see a clinician for ear pain, spreading redness or fever. Surveillance: the program will accept reports of new cases through March 25, two weeks after closure, and will notify the health officer of any case with onset after March 11.
References
Centers for Disease Control and Prevention. (2012). Principles of epidemiology in public health practice: An introduction to applied epidemiology and biostatistics (3rd ed.). U.S. Department of Health and Human Services.
Rasmussen, S. A., & Goodman, R. A. (Eds.). (2019). The CDC field epidemiology manual. Oxford University Press.
Ratnam, S., Hogan, K., March, S. B., & Butler, R. W. (1986). Whirlpool-associated folliculitis caused by Pseudomonas aeruginosa: Report of an outbreak and review. Journal of Clinical Microbiology, 23(3), 655-659. https://doi.org/10.1128/jcm.23.3.655-659.1986
How this MN505 Unit 4 example is structured
Numbered sections follow the order in which the work was done, so a reader can see that no conclusion came before its evidence. Preparation and verification open the memo: an urgent care clinician's photos and one lesion culture confirm the diagnosis before anyone counts cases. Establishing the outbreak takes one sentence, since the expected number of rash illnesses at one hotel on one weekend is zero. The case definition comes next, with person, place and time stated and the rash described without requiring a culture. Case finding uses the meet's registration list, which is why 64 guests appear and not just those who called. Descriptive work precedes the hypothesis, and the analytic comparison precedes the environmental results, so the laboratory finding confirms rather than creates the conclusion. Control measures, a note on communicating with families and a surveillance window close the memo.
Get an MN505 Unit 4 example written to your instructions
Most Unit 4 scenarios arrive as a line list or a narrative with onset times. Pass along whichever yours is, with the memo instructions and the rubric, and the investigation is written up in the sequence your course expects, rates calculated from the roster. It comes as the free first custom sample, returned in 24-48h. The paper above is an original model document written by our desk, not a submitted student paper and not an official Purdue University Global document.
MN505 Unit 4 questions, answered
Does the memo have to follow the investigation steps in exact order?
Field guidance notes that real investigations overlap, and control measures often start before analysis finishes. A memo, though, is easier to grade when its sections follow the logical sequence, because the reader can check that each conclusion rests on earlier evidence. The example says in one line that the spa was closed on day one as a precaution, then presents the evidence in order.
Why does the example keep the two pool-only cases in their group?
Because reassigning them to the hot tub group without evidence would inflate the association and hide a question worth asking. The memo notes that one of the two shared towels with a sibling who soaked, and the other may have misremembered. Reporting them honestly, with a sentence on misclassification, is stronger than a cleaner table built on guesswork.
How wide should the bins on the onset histogram be?
Field epidemiology texts commonly suggest an interval between an eighth and a third of the usual incubation period. Hot tub folliculitis tends to appear within a day or two of exposure, so six-hour bins show the shape without scattering cases thinly. The example counts hours from each guest's first soak rather than calendar time, because arrivals were spread across Friday and Saturday.