Multisystem Processes & Disorders

Measles, mumps, rubella: recognition and reporting

Clinical Overview and When to Suspect Measles, Mumps, or Rubella

— Febrile rash + cough/coryza/conjunctivitis → measles until proven otherwise

— Bilateral or unilateral parotid swelling with fever → mumps

— Mild diffuse rash + posterior auricular/suboccipital lymphadenopathy ± arthralgia (especially in a pregnant woman or her contact) → rubella

— Any of the above in an unvaccinated patient, recent international traveler, or known outbreak contact

Why these still matter on Step 3: declining MMR coverage, global travel, and community outbreaks have re-introduced these viruses into US primary care. All three are nationally notifiable and require immediate public health action.

Measles (rubeola): paramyxovirus, most contagious infection known (R0 12–18), airborne droplet nuclei persisting up to 2 hours after the patient leaves a room. Incubation 7–14 days; infectious 4 days before to 4 days after rash onset.

Mumps: paramyxovirus (Rubulavirus), spread by respiratory droplets/saliva. Incubation 12–25 days; infectious from 2 days before to 5 days after parotitis onset.

Rubella (German measles): togavirus, droplet spread, incubation 14–21 days. Mild in adults but devastating in pregnancy (congenital rubella syndrome, CRS).

When to suspect in clinic:

Step 3 management: the moment you suspect measles, isolate in a negative-pressure (airborne) room, mask the patient, notify infection control AND the local health department by phone the same day — do not wait for confirmatory serology. Reporting is mandatory in all 50 states.

Board pearl: US measles cases in unvaccinated children clustered around philosophical/religious exemption communities and post-pandemic catch-up gaps. A child returning from Europe, the Philippines, or sub-Saharan Africa with fever and rash is the prototypical stem.

Key distinction: roseola and erythema infectiosum cause rash after defervescence; measles rash appears while the patient is still febrile and toxic-appearing.

Presentation Patterns and Key History

— Prodrome (2–4 days): high fever (often >103°F/39.4°C), the "3 C's" — cough, coryza, conjunctivitis — plus malaise. Patients look genuinely sick.

— Enanthem: Koplik spots — 1–2 mm bluish-white papules on erythematous buccal mucosa opposite the molars, appearing 1–2 days before rash, pathognomonic but fleeting.

— Exanthem: erythematous maculopapular, blanching rash starting on the forehead/hairline and behind the ears, spreading cephalocaudally to trunk and extremities over 3 days, becoming confluent and then desquamating with brownish discoloration.

— Vaccination status with dates and doses of MMR (need 2 doses for full immunity in children; 1 dose ~93% effective for measles, 2 doses ~97%)

— Recent international travel or known measles/mumps outbreak exposure (school, congregate setting, healthcare worker)

— Pregnancy status in any rubella-like illness, and rubella exposure in pregnant contacts

— Immunocompromise (HIV, chemotherapy, biologics)

Measles classic 3-stage course:

Mumps: low-grade fever, myalgia, anorexia → parotitis (bilateral in ~70%) with earache worsened by chewing/citrus; Stensen duct erythema. May present with orchitis (post-pubertal males, ~30%), oophoritis, aseptic meningitis, or pancreatitis as the first clue.

Rubella: often subclinical (up to 50%). Pink, fine maculopapular rash starting on the face and spreading rapidly; tender posterior auricular, suboccipital, and posterior cervical lymphadenopathy is the highest-yield finding. Forchheimer spots (palatal petechiae) are nonspecific. Polyarthralgia/arthritis common in adult women.

High-yield history questions:

Board pearl: Koplik spots + cephalocaudal rash in an unvaccinated child returning from abroad → measles, full stop. Don't wait for IgM.

Key distinction: mumps parotitis is viral and bilateral; bacterial (suppurative) parotitis is unilateral with purulent Stensen duct drainage in a dehydrated elderly patient.

Physical Exam Findings and Severity Assessment

— Vitals: persistent high fever; tachypnea or hypoxia suggests measles pneumonia (leading cause of measles death in children)

— HEENT: bilateral nonpurulent conjunctivitis with photophobia, clear rhinorrhea, Koplik spots (look quickly — gone within 24–48 hrs of rash)

— Skin: blanching, confluent maculopapular rash progressing head→toe; in dark skin, look for textural change and post-inflammatory hyperpigmentation

— Neuro: altered mental status, ataxia, or seizures → acute disseminated encephalomyelitis (ADEM) or measles encephalitis (1 in 1000)

— Abdomen: hepatosplenomegaly uncommon — if present, reconsider diagnosis

— Parotid swelling that obscures the angle of the mandible and lifts the earlobe upward and outward

— Erythema and edema at Stensen duct orifice; no purulence

— Testicular exam in post-pubertal males: unilateral swelling, tenderness, warmth → orchitis (4–10 days after parotitis)

— Neuro: nuchal rigidity, Kernig/Brudzinski → aseptic meningitis (~10%)

— Rash is finer and paler than measles, spreads faster (face to feet in 24 hr), and clears in the order it appeared

— Palpate posterior auricular, suboccipital, posterior cervical nodes — tender, mobile

— Small joints (MCPs, wrists, knees) in adult women: symmetric arthritis mimicking early RA

Measles exam priorities:

Mumps exam:

Rubella exam:

Hemodynamic/severity flags: hypoxia, dehydration from poor oral intake (especially toddlers with mumps unable to swallow), signs of secondary bacterial superinfection (otitis media, pneumonia with focal consolidation).

CCS pearl: for a hospitalized measles patient, your initial order set is airborne isolation, IV fluids, vitamin A, pulse oximetry, CXR if respiratory symptoms, and notify public health — before any specific antiviral consideration.

Board pearl: an adult woman with a mild rash and wrist/knee arthritis after a daycare exposure → rubella, check IgM and pregnancy status.

Diagnostic Workup — Initial Labs and Confirmatory Testing

— Serum measles IgM (best initial test ≥3 days after rash onset; may be falsely negative if drawn too early)

— Measles RT-PCR on nasopharyngeal/throat swab AND urine (highest yield within first 3 days of rash; preferred by public health for genotyping)

— Acute + convalescent IgG (4-fold rise) confirms recent infection

— Adjunctive: CBC often shows leukopenia and lymphopenia; LFTs mildly elevated; CXR if respiratory symptoms

— Mumps IgM serology PLUS RT-PCR of buccal/parotid duct swab (massage gland for 30 sec before swabbing) within 3 days of parotitis onset — best yield

— Serum amylase elevated (parotid source, not pancreatic unless lipase also up)

— In vaccinated patients, IgM is frequently negative — PCR is essential; do not rule out mumps based on negative IgM in a vaccinated person

— If meningitis suspected: LP shows lymphocytic pleocytosis, normal/low glucose, elevated protein

— Rubella IgM (turns positive ~5 days after rash) + IgG acute/convalescent

— RT-PCR on throat swab, nasal swab, or urine

— In pregnancy: confirm with IgG avidity testing — low avidity suggests recent primary infection (highest CRS risk)

Do not delay isolation or reporting while awaiting results. Testing strategy depends on suspected pathogen and timing relative to rash/symptom onset.

Measles:

Mumps:

Rubella:

Step 3 management: call the state/local health department before sending tests — they often want specimens sent to a public health lab for genotyping, and they can expedite results. Commercial lab IgM has imperfect sensitivity/specificity in low-prevalence settings.

Key distinction: a positive IgM in a low-prevalence setting has a poor PPV. Public health confirmation (PCR + epi link) is what counts for case classification.

Board pearl: in any febrile rash, always ask about pregnancy and check β-hCG before further workup — rubella diagnosis in pregnancy triggers urgent OB/MFM and infectious disease referral.

Diagnostic Workup — Advanced and Population-Specific Studies

— Rubella IgM in infant serum (does not cross placenta — IgM = infant production = infection)

— Persistence of rubella IgG beyond 6–12 months of age (passive maternal IgG should wane)

— RT-PCR of nasopharyngeal swab, urine, CSF

— Targeted evaluation: echocardiogram (PDA, peripheral pulmonic stenosis), ophthalmologic exam (cataracts, salt-and-pepper retinopathy, glaucoma), auditory brainstem response (sensorineural hearing loss), head US/MRI (microcephaly, intracranial calcifications), CBC (thrombocytopenia, "blueberry muffin" purpura)

— Progressive cognitive decline, myoclonus, seizures in adolescent

— EEG: periodic Rademecker complexes (high-amplitude bursts every 4–15 sec)

— CSF: elevated measles IgG with high CSF:serum antibody ratio

— MRI: white matter changes, atrophy

— Orchitis: scrotal ultrasound to exclude torsion if presentation atypical

— Suspected pancreatitis: lipase (more specific than amylase, which is already elevated from parotitis)

— Hearing loss: audiometry (sudden sensorineural)

— Encephalitis: MRI + LP

— Susceptible contacts: birth year ≥1957 without documented 2 MMR doses or lab evidence of immunity → check measles/mumps/rubella IgG; if negative or equivocal, treat as susceptible

— Healthcare workers without immunity must be furloughed from day 5 after first exposure through day 21 after last exposure

Congenital rubella syndrome (CRS) workup in a newborn:

Subacute sclerosing panencephalitis (SSPE) — late measles complication, 7–10 years after primary infection:

Mumps complications workup:

Outbreak-context contact tracing tests:

CCS pearl: if a pregnant woman is exposed to rubella, draw IgG immediately; if positive → immune, reassure. If negative → repeat IgM/IgG in 3–4 weeks and consider amniocentesis with PCR after 21 weeks gestation.

Board pearl: an adolescent with declining school performance, jerks, and prior measles in infancy = SSPE; remember EEG findings.

Risk Stratification and First-Line Management Logic

— High-risk hosts (require aggressive monitoring/possible admission): infants <12 months, pregnant women, immunocompromised (HIV with low CD4, post-transplant, chemotherapy, high-dose steroids, biologics), malnourished, vitamin A deficient

— Standard-risk: healthy children >12 months and immunocompetent adults

— Outpatient with home isolation for uncomplicated measles/mumps/rubella in immunocompetent patients — instruct strict isolation through infectious period, no school/work/healthcare visits except for emergencies (call ahead)

— Admit for: respiratory distress, dehydration unresponsive to oral fluids, encephalitis/meningitis signs, orchitis with severe pain or systemic toxicity, immunocompromised host, any pregnant woman with measles

— Negative-pressure airborne isolation for measles inpatients; droplet precautions for mumps and rubella

— Antipyretics (acetaminophen; avoid aspirin in children)

— Hydration — oral preferred, IV if poor intake

— Eye care for measles (cool compresses, avoid bright light)

— Scrotal support, ice, NSAIDs for mumps orchitis

— MMR vaccine within 72 hr for measles exposure (preferred in immunocompetent ≥6 months)

— Immune globulin (IG) within 6 days for high-risk contacts who cannot receive vaccine: infants <12 months, pregnant women without immunity, severely immunocompromised

– IGIM 0.5 mL/kg (max 15 mL) or IGIV 400 mg/kg

Risk stratification at the index visit:

Disposition decision tree:

Supportive care core (all three):

Post-exposure prophylaxis (PEP) for susceptible contacts — within first 72 hours of exposure:

Step 3 management: the single most consequential outpatient action is calling the health department; they coordinate contact tracing, PEP distribution, and exposure assessment in schools/workplaces. Document the call.

Board pearl: vaccine within 72 hr beats IG when both are options, but IG is preferred when vaccine is contraindicated (pregnancy, immunocompromise, infants <6 months).

Pharmacotherapy — Disease-Specific and Adjunctive Treatment

— Reduces morbidity and mortality, especially ophthalmologic complications

— Dosing by age, once daily for 2 consecutive days, repeat at 4 weeks if signs of vitamin A deficiency:

– <6 months: 50,000 IU

– 6–11 months: 100,000 IU

– ≥12 months: 200,000 IU

— Mechanism: restores epithelial integrity, supports immune function

— Orchitis: NSAIDs, ice, scrotal elevation; corticosteroids do not prevent infertility despite older teaching — avoid routine use

— Aseptic meningitis: supportive; usually self-limited

— Arthralgia: NSAIDs

— No specific therapy alters outcome in CRS once established — prevention via immunization is the only effective strategy

— Live attenuated combination

— Schedule: dose 1 at 12–15 months, dose 2 at 4–6 years

— Contraindications: pregnancy (avoid 4 weeks before and during), severe immunodeficiency (HIV with CD4 <15% or <200, post-HSCT, primary immunodeficiency), anaphylaxis to neomycin or gelatin

— OK in egg allergy (despite older teaching), OK in HIV if CD4 ≥15%/≥200

— Adverse effects: fever 7–12 days post-vaccination, transient rash, mild arthralgia (especially adult women with rubella component), rare thrombocytopenia, febrile seizures (slightly increased risk at 12–23 months, especially with MMRV combination)

No specific antiviral exists for measles, mumps, or rubella. Management is supportive + targeted adjuncts + immune-based PEP.

Vitamin A for measles (WHO/AAP recommended for all children with measles in the US, not just developing countries):

Immune globulin for PEP (covered in chunk 6); not therapeutic once disease is established.

Mumps adjuncts:

Rubella adjuncts:

MMR vaccine pharmacology (high-yield):

Step 3 management: before giving MMR, ask about pregnancy, immunosuppression, recent blood products (defer 3–11 months after IG depending on product), and TB skin testing (place same day or wait 4 weeks).

Board pearl: vitamin A is the only specific pharmacotherapy that changes measles outcomes — give it to every child with measles.

Public Health Response and Outbreak Management

— Measles: immediately by phone to local/state health department on clinical suspicion (do not wait for labs) — this is among the fastest reporting requirements in US public health

— Mumps and rubella: within 24 hours of suspicion (varies slightly by state)

— Congenital rubella syndrome: immediately

— Symptom onset date, rash onset date

— Vaccination history with dates

— Travel history (60-day window for measles)

— Setting exposures: school, daycare, healthcare, congregate housing, air travel

— List of close contacts in infectious period

— Identify all contacts during patient's infectious period (measles: 4 days before to 4 days after rash; mumps: 2 days before to 5 days after parotitis; rubella: 7 days before to 7 days after rash)

— Assess immunity (2 documented MMR doses, lab evidence of immunity, lab-confirmed prior infection, or birth before 1957 — except healthcare workers and pregnant women)

— Administer PEP within appropriate windows

— Exclude susceptible non-immune contacts from school/daycare/work for 21 days after last exposure (measles), 25 days (mumps), 23 days (rubella)

— All HCWs require 2 documented MMR doses or lab immunity regardless of birth year

— Exposed susceptible HCWs: furlough as above

— Symptomatic HCWs: immediate work exclusion + testing

— Triage protocols: any febrile rash → mask and place in private room with door closed, ideally negative pressure for measles

— Notify infection prevention before patient enters waiting area

Mandatory reporting timeline:

Case investigation elements (the health department will ask):

Contact tracing and PEP coordination:

Healthcare worker management:

Infection control in clinic:

CCS pearl: in a CCS case of suspected measles, the orders that score points are airborne isolation, notify infection control, notify state health department, measles IgM, measles PCR (NP and urine), vitamin A, CBC, supportive care — in that approximate order.

Board pearl: failure to report a notifiable disease can result in fines and license action; reporting is not a HIPAA violation — public health is an explicit permitted disclosure.

Special Populations — Elderly, Immunocompromised, and Renal/Hepatic

— Reinfection or modified illness can occur, especially with mumps (vaccine-induced antibody wanes by 10–15 years post-dose 2)

— During outbreaks, ACIP recommends a third MMR dose for persons at increased mumps risk (e.g., outbreak settings, close-contact congregate environments)

— Severe immunosuppression (HIV with CD4 <200 or <15%, hematologic malignancy on active therapy, solid organ transplant within 2 years, HSCT within 24 months, biologics like rituximab, high-dose steroids ≥20 mg prednisone-equivalent ≥14 days): MMR contraindicated — use IG for PEP

— HIV with CD4 ≥200 and ≥15%: MMR is safe and recommended

— Severe measles in immunocompromised: prolonged shedding, giant cell pneumonia, measles inclusion-body encephalitis — high mortality; consider IV/inhaled ribavirin in consultation with ID (off-label, weak evidence)

— MMR is safe in CKD/dialysis (not live-virus contraindicated by renal status alone)

— Vitamin A dosing for measles: no renal adjustment needed for short-course

— MMR safe; monitor LFTs in acute measles (transaminitis common, usually self-resolving)

— Avoid hepatotoxic antipyretic excess

Adults born before 1957: generally considered immune to measles, mumps, and rubella by natural infection; exception: healthcare workers, pregnant women, and individuals planning international travel — these groups should have documented immunity or receive MMR regardless of birth year.

Older adults with waning immunity:

Immunocompromised patients — both higher risk for severe disease and special vaccine considerations:

Chronic kidney disease and dialysis:

Chronic liver disease:

Step 3 management: before starting biologics (TNF inhibitors, rituximab) or planning organ transplant, screen MMR immunity and vaccinate susceptible patients ≥4 weeks before immunosuppression — a classic preventive medicine board question.

Board pearl: in an HSCT recipient, revaccinate with MMR ≥24 months post-transplant if no active GVHD and off immunosuppression — they lose donor-derived immunity.

Key distinction: "immunocompromised" is not monolithic — HIV with preserved CD4 is not a contraindication to MMR.

Special Populations — Pregnancy, Pediatrics, and Travel

— MMR contraindicated during pregnancy and 4 weeks before conception (theoretical risk; no documented CRS from inadvertent vaccination, but precaution stands)

— Screen rubella immunity at first prenatal visit; if non-immune, vaccinate postpartum before discharge — do not delay for breastfeeding (MMR is safe with breastfeeding)

— Rubella exposure during pregnancy:

– <12 weeks gestation: up to 85% CRS risk

– 13–16 weeks: ~50% with hearing loss primary defect

– >20 weeks: minimal risk

— Measles in pregnancy: increased risk of pneumonia, preterm birth, fetal loss — give IG (400 mg/kg IV) for PEP in non-immune pregnant contacts

— Mumps in pregnancy: associated with first-trimester spontaneous abortion; no specific congenital syndrome

— Routine MMR: dose 1 at 12–15 months, dose 2 at 4–6 years

— Accelerated schedule for travel/outbreak:

– Infants 6–11 months: give MMR as PEP/pre-travel; does not count toward routine schedule — still need 2 additional doses on schedule

– Children ≥12 months: can give dose 2 as early as 4 weeks after dose 1

— Infants <6 months: rely on maternal antibodies + IG if exposed

— MMRV (with varicella): slightly higher febrile seizure risk for dose 1 at 12–15 months; AAP/ACIP prefer separate MMR + varicella for dose 1, MMRV acceptable for dose 2

— All travelers ≥6 months should be age-appropriately MMR-immune before departure

— Counsel especially for Europe, Africa, Middle East, parts of Asia where measles is endemic

Pregnancy:

Pediatrics:

International travelers (high-yield Step 3 outpatient scenario):

CCS pearl: for a postpartum patient identified as rubella non-immune on prenatal labs, your discharge order set must include "MMR vaccine before discharge" plus counseling to avoid pregnancy for 4 weeks.

Board pearl: an infant 6–11 months traveling internationally gets one dose of MMR pre-travel and still needs the standard 2-dose series after 12 months.

Complications and Adverse Outcomes

— Otitis media (most common, 7–9%)

— Pneumonia (1–6%) — primary measles giant-cell pneumonia or secondary bacterial (S. pneumoniae, S. aureus, H. influenzae); leading cause of measles death

— Diarrhea/dehydration (8%)

— Acute encephalitis (~1 in 1,000) — days after rash; mortality 15%, neurologic sequelae 25%

— ADEM — post-infectious autoimmune demyelination, weeks later

— SSPE — 7–10 years later, uniformly fatal; risk ~1 in 10,000 (higher if infected <2 years old)

— Immune amnesia — measles erases immunologic memory for 2–3 years, increasing susceptibility to other infections

— Orchitis (30% of post-pubertal males, usually unilateral) — sterility uncommon (~13% subfertility); bilateral orchitis rare

— Oophoritis (~5% post-pubertal females), mastitis

— Aseptic meningitis (1–10%) — usually benign

— Encephalitis (rare, <0.1%) — higher mortality

— Sensorineural hearing loss — historically a leading cause of acquired deafness in children; usually unilateral, sudden

— Pancreatitis (~4%)

— Spontaneous abortion if infected in first trimester

— Arthritis/arthralgia (up to 70% of adult women)

— Thrombocytopenia (rare)

— Encephalitis (rare, ~1 in 6,000)

— CRS — the catastrophic outcome:

– Classic triad: sensorineural deafness, cataracts, congenital heart disease (PDA, peripheral pulmonic stenosis)

– Plus: microcephaly, intellectual disability, "blueberry muffin" rash (dermal erythropoiesis), hepatosplenomegaly, thrombocytopenia, late-onset diabetes mellitus

Measles complications (1 in 4 cases overall, higher in <5 yo and adults):

Mumps complications:

Rubella complications:

Step 3 management: any measles patient with new headache, altered mental status, or focal neuro findings → admit, neuro consult, LP if no contraindication, MRI brain — encephalitis until proven otherwise.

Board pearl: unilateral sudden sensorineural hearing loss in an adolescent during a mumps outbreak — get audiometry and report the case; hearing loss may be permanent.

When to Escalate Care — Admission and Consultation Triggers

— Hypoxia (SpO2 <92% on room air) or respiratory distress → likely pneumonia

— Dehydration unable to tolerate PO

— Neurologic signs (altered MS, seizures, focal deficits) → encephalitis workup

— Immunocompromised host (low threshold)

— Pregnant patient

— Infants <12 months with significant symptoms

— Severe orchitis with intractable pain or systemic toxicity

— Meningitis/encephalitis signs

— Pancreatitis with significant volume depletion or pain control failure

— Sudden hearing loss (ENT consult, audiology, possible steroid trial)

— Encephalitis (rare)

— Pregnant patient with confirmed primary infection — MFM consult, multidisciplinary planning

— Neonate with suspected CRS — NICU admission, multispecialty workup

— Infectious disease: any complicated case, immunocompromised host, suspected SSPE, considering ribavirin

— Public health/epidemiology: every case (mandatory)

— Infection prevention: confirm isolation protocols, exposure assessment within facility

— OB/MFM: pregnant exposure or infection

— Pediatrics/Neonatology: suspected CRS

— ENT/Audiology: mumps hearing loss

— Ophthalmology: measles keratitis or CRS cataract evaluation

— Neurology: encephalitis, ADEM, SSPE

— Respiratory failure requiring mechanical ventilation (measles pneumonia in immunocompromised)

— Status epilepticus or severe encephalitis

— Hemodynamic instability from secondary bacterial sepsis

Admit for measles when:

Admit for mumps when:

Admit for rubella when:

Consultations to consider:

ICU criteria:

CCS pearl: for an admitted measles patient who deteriorates with new hypoxia and bilateral infiltrates, your orders should include upgrade to ICU, ID consult, blood/sputum cultures, empiric antibiotics for superinfection (e.g., ceftriaxone + vancomycin if severe), and reassess vitamin A dosing.

Board pearl: the most common cause of death in measles is pneumonia; in mumps it's encephalitis; in rubella postnatally it's exceedingly rare — but CRS is the lethal entity to fear.

Key Differentials — Same-Category Viral Exanthems

— School-age child, "slapped-cheek" facial rash then lacy reticular rash on extremities

— Rash appears after systemic symptoms resolve

— Concerns: aplastic crisis in sickle cell, hydrops fetalis in pregnancy (especially <20 wk)

— Infant/toddler with high fever for 3–5 days, then defervescence followed by rash (rose-pink macules on trunk)

— Child looks well during fever; classic febrile seizure trigger

— Distinguishing feature: rash appears as fever breaks, opposite of measles

— Oral ulcers (anterior tongue, buccal — not Koplik), vesicles on palms/soles, perioral and perianal lesions

— Mild fever, very contagious in daycare

— Sandpaper rash, circumoral pallor, Pastia lines in skin folds, strawberry tongue, exudative pharyngitis

— Treat with penicillin; not viral — but a classic mimic on board stems

— Adolescent with fever, exudative pharyngitis, posterior cervical lymphadenopathy, splenomegaly

— Rash if given amoxicillin

— Mimics mumps if parotid-area swelling, but tonsillopharyngitis predominates

— Morbilliform rash, often without prodrome's "3 Cs"

— Look for DRESS features: eosinophilia, LFT elevation, lymphadenopathy

— ≥5 days fever + 4 of 5: bilateral nonexudative conjunctivitis, red cracked lips/strawberry tongue, polymorphous rash, extremity changes (palmar erythema, periungual desquamation), cervical lymphadenopathy ≥1.5 cm

— Critical mimic of measles — but Kawasaki lacks Koplik spots and cough/coryza

Erythema infectiosum (Fifth disease, parvovirus B19):

Roseola infantum (HHV-6/7):

Hand-foot-mouth disease (coxsackievirus A16, enterovirus 71):

Scarlet fever (group A strep):

Infectious mononucleosis (EBV):

Drug eruption (especially anticonvulsants, sulfa, amoxicillin):

Kawasaki disease:

Key distinction: measles = fever still present when rash appears, with the 3 Cs; roseola/fifth disease = rash after defervescence.

Board pearl: Kawasaki versus measles is the highest-yield differential — Kawasaki needs IVIG and aspirin urgently to prevent coronary aneurysms; missing it harms the patient.

Key Differentials — Non-Viral and Other-Category Causes

— Bacterial (suppurative) parotitis: dehydrated elderly/post-op patient, S. aureus, unilateral, purulent Stensen drainage, treat with antibiotics + hydration

— Sialolithiasis: intermittent post-prandial swelling, palpable stone, no fever

— HIV-associated parotid lymphoepithelial cysts: bilateral, painless, in HIV patient

— Sjögren syndrome: bilateral chronic parotid enlargement + sicca symptoms

— Lymphoma or salivary gland tumor: progressive painless mass; persistent → imaging and biopsy

— Other viruses causing parotitis: EBV, CMV, influenza, parainfluenza, HIV, coxsackie — clinically indistinguishable, distinguish by PCR/serology

— Drug rash, enterovirus, scarlet fever, fifth disease, secondary syphilis, Zika, dengue, chikungunya

— Zika in pregnancy: causes congenital microcephaly + cerebral calcifications, distinguish via travel history and Zika PCR

— Secondary syphilis: rash on palms and soles, mucous patches, condyloma lata — check RPR

— Rocky Mountain spotted fever: febrile rash starting wrists/ankles → centripetal, history of tick exposure, doxycycline empirically

— Meningococcemia: petechial/purpuric rash, fulminant — different rash morphology

— Toxic shock syndrome (staph or strep): diffuse erythroderma, hypotension, multiorgan involvement, desquamation later

— Stevens-Johnson syndrome/TEN: mucosal involvement, target lesions, drug history

Mumps differential (parotid swelling):

Rubella differential:

Measles differential broadened:

Step 3 management: in any febrile-rash patient, ask about tick exposure, drug exposure, sexual history, travel, and animal contact — these branches dramatically change empiric therapy (doxycycline for RMSF, ceftriaxone for meningococcemia, IVIG for Kawasaki/TSS).

Key distinction: rashes that start on extremities and move centrally (RMSF, secondary syphilis on palms/soles) are different from measles, which starts centrally (face/hairline) and moves peripherally.

Board pearl: when a stem says "rash on palms and soles," think secondary syphilis, RMSF, hand-foot-mouth, or Kawasaki — not measles.

Secondary Prevention, Vaccination, and Long-Term Plan

— Routine MMR: dose 1 at 12–15 months, dose 2 at 4–6 years; achieves ~97% measles, ~88% mumps, ~97% rubella protection

— Adult catch-up: anyone born ≥1957 without documented immunity → 1 dose (general population) or 2 doses (HCWs, students at post-secondary institutions, international travelers, household contacts of immunocompromised)

— Measles survivors: counsel about immune amnesia — increased susceptibility to other infections for 2–3 years; ensure all other routine vaccinations are up to date and adhered to

— Children recovering from measles: monitor growth, hearing (post-otitis), and neurodevelopmental milestones for SSPE late risk (rare but real)

— Mumps survivors: post-orchitis testicular function monitoring; if bilateral orchitis, consider semen analysis 3–6 months later if fertility concerns

— Mumps hearing loss: usually permanent; refer for audiology, hearing aids, cochlear implant evaluation if profound

— Rubella in pregnancy → newborn: lifelong multidisciplinary CRS follow-up (cardiology, ophthalmology, ENT/audiology, neurology, endocrinology for late-onset DM)

— Ensure all household contacts are MMR-immune

— School/daycare exclusion until non-contagious

— Document immunity in EHR with vaccine dates or serology

— Build EHR prompts for MMR status at well-child visits, preconception counseling, prenatal first visit, pre-travel visits, pre-immunosuppression

— Vaccine exemption laws vary by state — counsel families on risks of declining vaccination using motivational interviewing

Primary prevention is the management:

Post-disease counseling and follow-up:

Household/community measures:

Health systems considerations:

CCS pearl: at discharge from a measles admission, your orders should include outpatient follow-up in 1–2 weeks, audiology referral if otitis media occurred, ensure MMR vaccination of susceptible household contacts, and confirm public health case reporting completed.

Board pearl: the single most cost-effective prevention strategy in family medicine is on-time MMR vaccination — herd immunity threshold for measles is ~95%.

Follow-Up, Monitoring, and Counseling

— Outpatient visit at 1–2 weeks after rash resolution

— Assess for resolving cough, hearing concerns (post-otitis), nutrition recovery (especially in young children)

— Repeat vitamin A dose at 4 weeks if signs of deficiency (xerophthalmia, malnutrition)

— Neurodevelopmental check in infants/toddlers

— Educate family about delayed SSPE — return for any cognitive/motor decline (rare)

— 2-week visit to confirm resolution of parotitis and any orchitis

— Audiometry if any hearing complaints during or after illness

— Semen analysis at 3–6 months only if bilateral orchitis and fertility concerns

— Reassure: most patients have full recovery

— Adult women with arthritis: NSAID course usually sufficient; reassess at 4 weeks

— Pregnant patient with confirmed rubella: serial fetal ultrasound, MFM management, neonatal evaluation at birth

— CRS infants: lifelong multispecialty surveillance (cardiology q6–12 months early on, annual audiology, ophthalmology, endocrinology screening for diabetes in adolescence)

— Isolation reinforcement during infectious period — clear written instructions with dates

— Contact notification: help family identify and notify exposed individuals (school, family, healthcare facilities)

— Vaccine catch-up: identify susceptible household members and schedule MMR

— Pregnancy counseling: if female of reproductive age receives MMR, avoid pregnancy for 4 weeks

— Future travel: confirm immunity before international trips

— Daily temperature, hydration status, respiratory symptoms, neuro changes

— Caregivers should call/return for: persistent fever >4 days after rash onset (think superinfection), respiratory distress, lethargy, dehydration, severe headache, neck stiffness

Post-acute measles follow-up:

Mumps follow-up:

Rubella follow-up:

Counseling pillars:

Monitoring parameters during illness:

Step 3 management: in the post-discharge transition, the highest-yield action is closed-loop confirmation that the local health department received the case report and has initiated contact tracing — document this in the chart.

Board pearl: rubella vaccine given to a non-immune postpartum woman before hospital discharge is a standard of care quality metric — Step 3 loves this.

Ethical, Legal, and Patient Safety Considerations

— Measles, mumps, rubella, and CRS are nationally notifiable; reporting to public health is a HIPAA-permitted disclosure under public health activities (45 CFR 164.512(b))

— Failure to report can result in licensure action and civil penalties; some states impose criminal liability

— Reporting does not require patient consent

— Parents may decline MMR; document discussion, risks (including transmission to vulnerable contacts), use motivational interviewing rather than coercion

— School vaccine mandates vary: all 50 states require MMR for school entry; medical exemptions universal, religious/philosophical exemptions vary by state

— During outbreaks, public health authorities may exclude unvaccinated children from school for the duration of the outbreak — this has withstood legal challenge

— Adolescent minors and confidential care: MMR generally requires parental consent except in emancipated minors or state-specific mature minor provisions

— Pregnant patients: counsel that MMR is contraindicated; document

— Highest-risk transition: a febrile-rash patient sitting in a crowded waiting room — implement triage masking and isolation at check-in

— Communicate isolation status clearly between ED → admitting team → consultants → environmental services

— At discharge, call the receiving facility (school nurse, daycare, PCP) to relay public health instructions

— Mandatory documented immunity for HCWs; non-immune HCWs must be furloughed during exposure window

— OSHA/CDC require employee health programs to maintain immunity records

— Outbreaks disproportionately affect under-vaccinated communities; address access barriers (cost, transportation, language) — Vaccines for Children (VFC) program provides free vaccines for eligible children

Mandatory reporting and HIPAA:

Vaccine refusal / parental autonomy:

Informed consent edge cases:

Patient safety in transitions of care:

Healthcare worker safety:

Equity considerations:

Step 3 management: if a parent refuses MMR for a child during a measles outbreak and the child has been exposed, you must (1) offer PEP, (2) document refusal, (3) report exposure to public health, and (4) inform school of exclusion period — not optional.

Board pearl: mandatory disease reporting is the most commonly tested ethics/legal item for this topic — public health > individual privacy in this domain.

High-Yield Associations and Rapid-Fire Facts

— Pathogen: paramyxovirus (genus Morbillivirus), single-stranded negative-sense RNA

— Transmission: airborne, R0 12–18

— Infectious period: 4 days before to 4 days after rash

— Pathognomonic: Koplik spots

— Rash direction: cephalocaudal

— Top complication causing death: pneumonia

— Late complication: SSPE (7–10 years later)

— Specific Rx: vitamin A

— Vaccine efficacy: 1 dose 93%, 2 doses 97%

— Pathogen: paramyxovirus (Rubulavirus)

— Transmission: droplet/saliva

— Infectious period: 2 days before to 5 days after parotitis

— Hallmark: parotitis lifting earlobe up and out

— Top complications: orchitis, aseptic meningitis, sensorineural hearing loss, pancreatitis

— Lab clue: elevated amylase (parotid)

— Vaccine: live attenuated, efficacy 88% (2 doses); wanes over time

— Pathogen: togavirus (Rubivirus), single-stranded positive-sense RNA

— Transmission: droplet

— Hallmark: posterior auricular/suboccipital lymphadenopathy + mild rash, adult arthritis in women

— Catastrophe: CRS — cataracts, sensorineural deafness, PDA/peripheral pulmonic stenosis, "blueberry muffin" rash

— First-trimester infection: up to 85% CRS risk

— US declared rubella eliminated in 2004, but global travel maintains risk

— Live attenuated, subcutaneous

— Schedule: 12–15 mo, 4–6 yr

— Contraindications: pregnancy, severe immunosuppression, anaphylaxis to neomycin/gelatin

— Safe in HIV with CD4 ≥200/≥15%

— Safe in egg allergy

— PEP: vaccine within 72 hr, IG within 6 days

Measles rapid-fire:

Mumps rapid-fire:

Rubella rapid-fire:

MMR vaccine rapid-fire:

Key distinction: measles = sick + descending rash + 3 Cs + Koplik; mumps = parotitis ± orchitis; rubella = mild rash + posterior nodes + arthritis (in pregnancy = disaster).

Board pearl: birth year 1957 is the immunity cutoff for the general US population (assumed immune); for HCWs and pregnant women, documentation is required regardless.

Board Question Stem Patterns

— Best next step: airborne isolation + notify public health + measles IgM/PCR + vitamin A

— Common distractors: start IV antibiotics, send home with reassurance, wait for serology before reporting

— Diagnosis: mumps orchitis (vaccine immunity wanes; outbreaks occur in vaccinated young adults)

— Best test: mumps RT-PCR on buccal swab (IgM may be negative in vaccinated patients)

— Management: supportive (NSAIDs, scrotal support, ice); report to public health; consider 3rd MMR dose in outbreak

— Best next step: rubella IgM now; repeat IgG/IgM in 3–4 weeks; refer to MFM; counsel about CRS risk

— Wrong answers: give MMR (contraindicated in pregnancy), reassure no risk

— Answer: administer MMR before hospital discharge; avoid pregnancy for 4 weeks; breastfeeding is OK

— Answer: immediately notify local/state health department by phone — before labs return

— Answer: draw measles IgG; if non-immune, give MMR within 72 hr; furlough from day 5 to day 21 after exposure

— Answer: MMR now; still needs 2-dose series after 12 months

Stem 1 — Classic measles: "A 4-year-old unvaccinated child returns from a 2-week trip to the Philippines with 4 days of fever to 104°F, cough, conjunctivitis, and runny nose. On day 5, an erythematous maculopapular rash appears on the forehead and behind the ears, spreading downward. Buccal exam shows bluish-white spots opposite the molars."

Stem 2 — Mumps orchitis: "A 19-year-old college student presents with 3 days of bilateral parotid swelling and now unilateral testicular pain and swelling. Vaccinated as a child."

Stem 3 — Rubella exposure in pregnancy: "A 28-year-old G1P0 at 10 weeks gestation reports her unvaccinated nephew was diagnosed with rubella 2 days ago. Her prenatal labs show rubella IgG negative."

Stem 4 — Postpartum rubella non-immunity: "Prenatal labs showed rubella IgG negative. Patient just delivered."

Stem 5 — Reporting: "Suspected measles in clinic. What is the next step?"

Stem 6 — Healthcare worker exposure: "An RN with one documented MMR dose is exposed to a measles patient."

Stem 7 — Infant traveler: "A 9-month-old will travel to Europe."

Board pearl: the most common wrong answer is waiting for confirmatory labs before reporting or isolating — Step 3 rewards immediate public health action.

One-Line Recap

High-yield bullet recaps:

The core teaching point: Measles, mumps, and rubella are vaccine-preventable, nationally notifiable diseases where clinical recognition triggers immediate isolation, immediate reporting, and immediate post-exposure prophylaxis — all before laboratory confirmation, with MMR vaccination as the central long-term prevention strategy.

Recognize: measles = fever + 3 Cs + Koplik + cephalocaudal rash; mumps = parotitis ± orchitis/meningitis; rubella = mild rash + posterior auricular lymphadenopathy + arthritis in adult women; CRS = cataracts + deafness + cardiac defects + "blueberry muffin."

Report: notify the local/state health department immediately by phone on clinical suspicion of measles (within 24 hr for mumps/rubella); reporting is HIPAA-permitted and mandatory — do not wait for serology. Place measles patients in airborne (negative-pressure) isolation; mumps and rubella in droplet precautions.

Respond: administer PEP within 72 hr (MMR vaccine) or 6 days (immune globulin) to susceptible contacts; give vitamin A to every child with measles (200,000 IU ×2 days if ≥12 months); supportive care otherwise (no specific antiviral exists).

Prevent: MMR at 12–15 months and 4–6 years; catch-up adults born ≥1957 without documented immunity (especially HCWs, travelers, students, pregnancy planners); screen rubella immunity at first prenatal visit and vaccinate non-immune patients postpartum before discharge; contraindicated in pregnancy and severe immunosuppression but safe in HIV with CD4 ≥200/≥15% and in egg allergy.

Board pearl: when in doubt, the right answer on Step 3 is "isolate, report, vaccinate susceptible contacts" — the public health response is the management.