NSG 323 Unit 3 communicable disease investigation example

Investigation of an Imported Measles Case: Classification, Infectious Period, and Contact Follow-Up Across Four Exposure Sites

Student Name

Department of Nursing, Herzing University

NSG 323: Community and Public Health Nursing

Instructor Name

February 3, 2026

Investigation of an Imported Measles Case: Classification, Infectious Period, and Contact Follow-Up Across Four Exposure Sites

How the Case Came to Attention

This composite case follows an investigation by a county health department, with dates set in February 2026 for illustration. On Saturday, February 14, at 6:10 p.m., an emergency department physician called the county's after-hours line to report a suspected case of measles. The patient, a 24-year-old adult with no record of measles vaccination, had returned on February 1 from three weeks of travel abroad. Fever began on February 9, followed by cough, runny nose, and red eyes. A rash began on the face on February 12 and spread to the trunk and limbs. The patient visited an urgent care clinic on February 13 and was sent home with a diagnosis of a viral illness, then came to the emergency department on February 14, where the triage nurse recognized the pattern and moved the patient to an airborne infection isolation room after about 40 minutes in the waiting area. The patient was not admitted and was sent home under isolation instructions.

Case Definition and Classification

The national surveillance case definition for measles requires a generalized maculopapular rash, a temperature of at least 101 degrees Fahrenheit, and cough, coryza, or conjunctivitis. A case meeting the clinical description is confirmed by laboratory evidence, such as a positive measles IgM antibody or detection of measles virus RNA, or by an epidemiologic link to a confirmed case. On February 16, the state laboratory reported positive results on both a throat swab tested for measles RNA and a serum IgM test. The case was classified as confirmed. Because the likely exposure period, 7 to 21 days before rash onset, which here was January 22 to February 5, overlapped the patient's time abroad, the case was also classified as internationally imported.

Before laboratory results were back, the case was handled as suspected. The response did not wait for confirmation, because the windows for preventing illness in contacts close within days.

Reporting

Measles is reportable immediately by telephone in this state, on suspicion and without waiting for a laboratory result. The emergency physician's call met that requirement. The urgent care clinic, which saw the patient a day earlier, did not report, because measles was not suspected. The county notified the state health department that evening, and the state notified the Centers for Disease Control and Prevention through its usual channels once the case was confirmed.

The Infectious Period

A person with measles is considered infectious from 4 days before rash onset through 4 days after, counting the day of rash onset as day 0 (McLean et al., 2013). With rash onset on February 12, the infectious period ran from February 8 through February 16. Working from fever onset on February 9 would have missed February 8, the day the patient attended a church service. Measles virus can linger in indoor air as long as two hours once an infectious person has gone, so exposure included anyone in the same indoor space during the patient's visit or up to two hours afterward.

The patient's activities during the infectious period were reconstructed in a phone interview on the evening of February 14: a Sunday church service on February 8; work in an open-plan office on February 9 and 10; home with a roommate from February 11; the urgent care visit on February 13; and the emergency department visit on February 14.

Contacts and Actions

Measures after exposure are time-limited. MMR vaccine given within 72 hours of exposure can prevent or modify disease, and immune globulin given within 6 days can do the same for people who cannot receive the vaccine, such as infants under 12 months, pregnant people without evidence of immunity, and people with severe immune compromise (McLean et al., 2013). By the time of the report, the vaccine window had closed for the church and office exposures, which is why the response concentrated on immunity checks, monitoring, and exclusion for those groups.

Evidence of Immunity and Exclusion

Each contact was assessed for presumptive evidence of immunity: documentation of two doses of measles-containing vaccine for adults at higher risk, such as health care personnel, and one dose for other adults; laboratory evidence of immunity or disease; or birth before 1957. Contacts without evidence of immunity who did not receive post-exposure prophylaxis were excluded from work, school, and child care from the 5th through the 21st day after their last exposure. Health care personnel without evidence of immunity were excluded for the same period whether or not they received vaccine. All contacts were given the symptoms to watch for and told to call ahead, not walk in, if symptoms began, so that a clinic could prepare an isolation room.

Protecting the Identity of the Case

Contact notification did not name the patient. Urgent care and emergency department contacts were told only that they had been in a location at a given time when a person with measles was present. At the office, the health department, not the employer, contacted coworkers directly; the employer was told the dates and floor involved, not the employee's name, and was reminded that the illness is private health information. The church notice gave the service time only. In a small workplace or congregation, people may guess who was ill, and staff were instructed never to confirm or deny a guess. Protecting the case is not only an ethical and legal duty; a case who feels exposed is less likely to cooperate with follow-up, and cooperation from the first case often determines whether an outbreak is contained (Gastañaduy et al., 2016).

Monitoring and Closure

The investigation remains open until 42 days, two full incubation periods, have passed after the last possible exposure without a new case. The last possible exposure outside the home was in the emergency department on February 14, and the roommate was exposed through February 16, the end of the infectious period. Counting 42 days from February 16, the investigation can close on March 30 if no secondary cases appear. The missed diagnosis at urgent care was reviewed, without blame, with the clinic's medical director, who agreed to post a travel and rash screening prompt at registration. Clinicians can use standard references on communicable disease control to review how measles presents and when to suspect it (Heymann, 2022).

References

Gastañaduy, P. A., Budd, J., Fisher, N., Redd, S. B., Fletcher, J., Miller, J., McFadden, D. J., Rota, J., Rota, P. A., Hickman, C., Fowler, B., Tatham, L., Wallace, G. S., de Fijter, S., Parker Fiebelkorn, A., & DiOrio, M. (2016). A measles outbreak in an underimmunized Amish community in Ohio. New England Journal of Medicine, 375(14), 1343-1354. https://doi.org/10.1056/NEJMoa1602295

Heymann, D. L. (Ed.). (2022). Control of communicable diseases manual (21st ed.). American Public Health Association.

McLean, H. Q., Fiebelkorn, A. P., Temte, J. L., & Wallace, G. S. (2013). Prevention of measles, rubella, congenital rubella syndrome, and mumps, 2013: Summary recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recommendations and Reports, 62(RR-04), 1-34.