NR 503 Week 6 Scabies Outbreak Investigation Paper Example

Reconstructing a Scabies Outbreak in a Composite Assisted Living Community From Four Files: Why the Pharmacy Date Made a Spike and the Itch Date Made a Slow Climb

Student Name

College of Nursing, Chamberlain University

NR 503: Population Health, Epidemiology and Statistical Principles

Instructor Name

Month Day, Year

Reconstructing a Scabies Outbreak in a Composite Assisted Living Community From Four Files: Why the Pharmacy Date Made a Spike and the Itch Date Made a Slow Climb

A Reconstruction, Stated as One

This write-up reconstructs an outbreak of scabies at Linden Court, a composite assisted living community with 96 residents, 24 of them in a secured memory care wing, and 70 employed staff. The community, the people and the figures are composite, built to illustrate the method. The outbreak was recognized on October 2, when a memory care resident admitted to hospital with a worsening rash was diagnosed with crusted scabies, a severe form in which a person can carry very large numbers of mites and is highly contagious. Her rash had been treated as eczema since July.

Nobody at Linden Court was counting cases before October 2, so everything that follows was pieced together afterward from records created for other purposes. The write-up begins with those records, because their purposes decide what they can show, and it follows the steps of an outbreak investigation as the CDC sets them out: confirm, define, count, describe by time, place and person, then look for what is missing (Centers for Disease Control and Prevention, 2012).

The Files and What Each Was Made For

Four files held information about possible cases:

1. The pharmacy dispensing log. Created for billing. Each row is a prescription filled, with the date dispensed. It records every resident treated with permethrin cream or ivermectin, but not when anyone started itching.

2. The weekly skin check log. Created by nursing for pressure injury prevention. Each row is a resident's weekly skin inspection, with a free-text field where nurses sometimes noted a rash or scratching, and the date of the check.

3. The staff occupational health file. Created for sick leave and workers' compensation. It records when an employee reported a skin complaint, and whether they were sent to their own clinician.

4. The dermatology referral records. Created by the visiting nurse practitioner's referral system. They record which residents had a skin scraping and when it was read, which gives confirmation but covers only 11 residents.

None of these files was designed to track an outbreak, and each carries its own date.

Which Date Column

The first epidemic curve, drawn by the facility the week after recognition, used the only date that appeared for every treated resident: the pharmacy dispensing date. It showed almost nothing through September, then 19 cases in the week of October 2 and 7 more the week after. That shape looks like a sudden point-source outbreak, as though something happened in late September that infested everyone at once.

That shape belongs to the reporting process, not to the illness. Almost no one was treated before October 2 because no one suspected scabies; once the index case was recognized, the facility examined everyone and treated in a single sweep. The dispensing date records when the facility noticed, not when residents were infested.

The second curve used a different date: the first recorded sign of itching or rash, taken from the skin check log for residents and from the occupational health file for staff, and confirmed by interviewing nurses and staff where the record was unclear. For 38 of the 45 people treated, a first-itch date could be established. Plotted on that date, the curve rises slowly from mid-August through September, with new cases every week and no single peak.

The Curve Read for Pattern

A slow, continuing rise with cases every week is the pattern of a propagated outbreak, spread from person to person rather than from one exposure. That fits scabies, which spreads by prolonged skin-to-skin contact. It also fits the timeline, once the incubation is used correctly. Federal guidance notes that in a person infested for the first time, symptoms typically take four to eight weeks to appear, though the person can spread mites before they itch (Centers for Disease Control and Prevention, 2024).

Working backward from the earliest itch dates in mid-August, the first secondary cases would have been infested in late June or July, which is when the index resident's rash began and was first treated as eczema. Worked backward from the dispensing dates, the same arithmetic would place the start of transmission in August, after the index case's rash was well established, and would have missed two months of spread. The same incubation window applied to the wrong date gives the wrong origin.

A Roster as Denominator

Counting cases is not enough; the counts need a population underneath them. The facility's census and staff schedule gave the denominators. Among residents, 14 of 24 in memory care were cases (58%), against 9 of 72 in assisted living (12.5%). Among staff, 11 of 70 were cases overall, but the difference by role was stark: 8 of the 12 aides who regularly bathed or dressed the index resident were cases (67%), compared with 3 of the other 58 staff (5%).

These attack rates point to the route. The highest rates were in people with the most hands-on contact with the index resident and among her neighbors on the memory care wing, where residents need help with bathing and dressing from the same small group of aides. The low rate in assisted living, where residents are more independent, fits spread through direct care rather than shared spaces. Control measures followed from that pattern: treating everyone in memory care and all hands-on staff at the same time, with a second dose where indicated, rather than treating only those with symptoms.

Cases No File Holds

The reconstruction is incomplete in ways the files cannot fix, and each gap has a direction.

Agency staff. Linden Court used agency aides on weekends. They were not on the employee roster and had no occupational health file, so any cases among them are missing from both numerator and denominator.

Families and visitors. Relatives who helped with care, especially in memory care, had hands-on contact and could have been infested. No file records them. Neither do household members of infested staff.

Residents who could not report. Several memory care residents could not tell anyone they itched. For them, the first-itch date depends on a nurse noticing scratching during a weekly skin check, which could be a week or more after onset. Their dates are likely too late.

Residents who left. Two residents moved to other facilities in September and one died. None was examined, and their new facilities were not told until the health department traced them.

These gaps mean the true size of the outbreak was larger than 45 cases and that the epidemic curve likely starts somewhat earlier than the records show. The practical conclusion for the facility is that a rash in a resident that does not respond to eczema treatment should prompt a skin scraping before the next weekly check, not after several months, and that the weekly skin check log should include a structured field for itching so that the next curve can be drawn from a date made for the purpose.

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.

Centers for Disease Control and Prevention. (2024). About scabies. https://www.cdc.gov/scabies/about/index.html