Primary Measles Encephalitis

**Background:** Measles is a highly infectious RNA virus that, despite being declared eliminated in the United States in 2000, has seen increasing prevalence due to rising rates of unvaccinated children. The recommended live-attenuated MMR vaccine schedule includes one dose at 12–15 months and a second at 4–6 years. Measles complications include otitis media, pneumonia, laryngotracheobronchitis, diarrhea, corneal ulceration, and central nervous system complications such as primary measles encephalitis, acute post-infectious measles encephalomyelitis, measles inclusion body encephalitis, and subacute sclerosing panencephalitis. Primary measles encephalitis occurs in approximately 1 out of every 1000 measles patients, with onset typically within seven days of the measles prodrome. Mortality is 10%–15%, and an additional 25% of survivors develop permanent neurodevelopmental sequelae. Treatment is largely supportive, but prompt recognition, airborne precautions, and transfer to a pediatric ICU are critical.

**Methods:** This is a simulation-based educational scenario designed for emergency medicine residents. The case involves a 5-year-old unimmunized female presenting with a 6-day history of fever, a 4-day history of a maculopapular rash starting on the forehead and spreading downward, and one day of confusion and headache. Vital signs on presentation: HR 155, BP 86/50, RR 24, temperature 104.2°F, O2 sat 98% on room air, weight 15 kg. The patient is drowsy but awakens to voice, with a GCS of 13 (E3V4M6). Physical exam reveals a brown maculopapular rash confluent on the face and upper trunk, mild nonpurulent conjunctivitis, and nuchal rigidity. No Koplik spots are visualized. The scenario unfolds with participants expected to place the patient on a monitor, obtain a point-of-care glucose, obtain immunization status, place the patient in airborne precautions, obtain consent for lumbar puncture, perform the lumbar puncture, administer a 20 cc/kg IV fluid bolus, and administer broad-spectrum antibiotics and antivirals (e.g., vancomycin, ceftriaxone, acyclovir) appropriate for age-specific pathogens to treat encephalitis. The patient's condition worsens (increased tachycardia and hypotension) if fluids and antibiotics are not given, and improves once they are administered. Transfer to a pediatric ICU is the final disposition. The session includes a debriefing and lecture. Feedback was collected from residents using a survey based on the DASH Student Version Short Form.

**Key Results:** The simulation was conducted with approximately ten emergency medicine residents during the 2019–2020 academic year. Feedback from five returned surveys was overwhelmingly positive, with an average score of 7 (consistently effective/very good or extremely effective/outstanding) across all categories. The only qualitative comment stated: “Great case with good learning points.” The debriefing discussions covered differential diagnoses of fever and rash, clinical presentation of measles, empiric treatment of meningitis/encephalitis, types and indications of isolation, and when to call for transfer to a pediatric center. The paper provides detailed lab results for the simulated patient: CBC shows WBC 15.4 x1000/mm3, Hgb 14.0 g/dL, HCT 35.7%, Plt 580 x1000/mm3. BMP shows BUN 27 mg/dL, Cr 1.1 mg/dL, glucose 90 mg/dL. CSF studies: appearance clear, glucose 60 mg/dL, protein 74 mg/dL, RBC 5–10/uL, WBC 400/uL, gram stain no organisms seen. Urinalysis shows ketones 2+. CT head and chest X-ray are normal. The paper also includes a detailed simulation events table outlining expected participant actions and corresponding patient vital sign changes.

**Clinical Implications:** This simulation-based educational tool effectively reinforces the critical management steps for primary measles encephalitis. The key clinical takeaway is that any patient with fever, rash, and altered mental status should prompt consideration of measles encephalitis, especially in unimmunized children. Immediate actions include placing the patient in airborne precautions (negative pressure room, N95 or PAPR), obtaining CSF via lumbar puncture (which typically shows lymphocytic pleocytosis and elevated protein), and initiating empiric broad-spectrum antibiotics and acyclovir while awaiting confirmatory testing (PCR throat swab and serum IgM measles antibodies). Vitamin A should be administered for severe cases (200,000 IU for children 12 months and older). The scenario highlights the importance of early fluid resuscitation and early transfer to a pediatric ICU, as mortality is 10%–15% and 25% of survivors have permanent neurodevelopmental sequelae. The paper also reviews isolation precautions: measles requires airborne precautions. It emphasizes reporting suspected cases to the local health department and considering post-exposure prophylaxis with MMR vaccine within 72 hours or immunoglobulin within six days for susceptible contacts. The simulation provides a cost-effective, psychologically safe environment for residents to practice these critical actions and receive formative feedback.