Measles (Rubeola)

Meet the patient

A four-year-old is brought in febrile, coughing, with streaming eyes and a sore red mouth the mother cannot explain. She has not been immunised — the family moved, the card was lost, the dose was never given. On the buccal mucosa opposite the lower molars are a few tiny bluish-white grains on a bright-red base, like grains of salt on a red carpet. The rash has not yet appeared.[1]

The two questions this child forces you to answer in the next hour are the two that decide every measles case: is this measles? (the Koplik spots answer yes, before the rash) and what do I do about the people she has coughed on? (isolation, notification, contact tracing and post-exposure prophylaxis answer that). Hold those two questions and every section below slots into place.[1]

One virus, one illness — why measles is the canary in the coal mine

Measles is one disease with one virus and one vaccine — and it is the most sensitive indicator of immunisation-programme performance anywhere it circulates. Where two-dose coverage is high, measles vanishes; where coverage dips even a few percentage points, measles returns first, because its extraordinary contagiousness exploits every pocket of susceptibility.[1]

The measles morbillivirus is an enveloped, negative-sense, single-stranded RNA virus of the family Paramyxoviridae, genus Morbillivirus. It is pleomorphic, roughly spherical, and about 150 to 300 nm across. Its genome encodes six structural proteins — nucleoprotein (N), phosphoprotein (P), matrix (M), fusion (F), haemagglutinin (H), and the large polymerase (L) — and two non-structural proteins, V and C, encoded within the P gene, which act as interferon antagonists. The H protein binds the host receptors CD150 (SLAM) on immune cells and nectin-4 on epithelium; the F protein fuses the viral envelope with the cell membrane. Because the virus is enveloped, soap, detergent, alcohol and UV destroy it — but it survives airborne for up to two hours in a room.[1]

Two facts dominate the clinical reasoning. First, its contagiousness is extraordinary — a basic reproduction number of 12 to 18 means one case in a susceptible community infects almost everyone exposed, and herd immunity needs about 95 percent two-dose coverage. Second, it is entirely preventable with the MMR vaccine (two doses give over 97 percent protection), so every case is a vaccination failure — missed, refused, or a broken cold chain. In exam terms, a single measles case in an "eliminated" region is an outbreak until proven otherwise.[1]

How common, who, and why coverage drives everything

Measles was once a near-universal childhood infection. Aggressive vaccination cut global deaths from an estimated 2.6 million per year in 1980 to fewer than 100,000 by the late 2010s, but falling coverage has reversed elimination in several regions — the Disneyland 2014 to 2015 outbreak, and the UK loss of elimination in 2018, are the case studies examiners quote.[1][8]

[1] [7]

The epidemiology is governed almost entirely by the R0 and the vaccination coverage. The herd-immunity threshold comes from H = 1 minus 1 over R0: with R0 of 12 to 18, between 91.7 and 94.4 percent of the population must be immune, and because one dose is about 93 percent effective and two doses about 97 percent, near-universal two-dose coverage is required. This is why measles is the first vaccine-preventable disease to resurge when immunisation weakens.[1][7]

The people measles finds first:[1]

• Unvaccinated children and adults — the dominant driver (missed vaccination, refusal, broken cold chain).
• Infants under 6 to 9 months — transplacental maternal antibody wanes, opening a susceptibility window before routine immunisation.
• Malnourished and vitamin-A-deficient children — severe disease, keratitis, blindness, high mortality; the dominant burden in the developing world.
• Immunocompromised hosts (HIV, primary immunodeficiency, transplant, chemotherapy) — severe atypical disease (giant-cell pneumonia, MIBE); live vaccine contraindicated.
• Pregnant women — higher risk of severe measles, miscarriage, premature labour, low birthweight; live vaccine contraindicated in pregnancy.
• Crowded settings — refugee camps, dormitories, schools, healthcare waiting rooms; explosive outbreaks.

[1] [2]

Transmission dynamics. The virus is shed from the respiratory tract during coughing, sneezing, talking and breathing; particles under 5 micrometres stay airborne for up to two hours. The patient is contagious from 4 days before the rash to 4 days after it appears — most infectious in the prodrome, when the diagnosis is least obvious. The incubation period averages 10 to 14 days (range 7 to 21). Seasonality is late winter and spring in temperate climates, year-round with monsoon peaks in the tropics.[1][2]

The cascade — entry, two viraemias, and why the rash is immune clearance

Measles binds CD150 (SLAM) on activated immune cells and nectin-4 on epithelium, then replicates in regional lymphoid tissue. Because it replicates in the very immune cells that should control it — dendritic cells, macrophages, lymphocytes — it hijacks its own transport system, and its V and C proteins antagonise interferon so it outruns adaptive immunity. Nectin-4 is also expressed on many cancer cells, which is why attenuated measles is being developed as an oncolytic vector.[1]

The cascade runs in stages:[1]

1. Entry and local replication (days 0 to 3) — virus infects respiratory epithelium and alveolar macrophages, then drains to regional lymph nodes.
2. Primary viraemia (days 2 to 3) — infected lymphocytes and monocytes carry virus to the reticuloendothelial system (spleen, lymph nodes, liver, thymus).
3. Secondary viraemia (days 5 to 7) — virus seeds the skin, conjunctivae, respiratory tract, gut and other epithelial surfaces; symptoms escalate.
4. Warthin-Finkeldey giant cells — pathognomonic histology: multinucleated giant cells (fused infected epithelial and lymphoid cells) carrying viral inclusions, found in lymphoid tissue, respiratory epithelium and Koplik-spot lesions.
5. Rash (about day 14, 4 days after prodrome onset) — a cell-mediated (type IV) attack by cytotoxic T lymphocytes on measles-infected capillary endothelial and epithelial cells. The rash reflects immune clearance, not direct viral damage — which is why an immunocompromised host may have no rash yet severe disease, and why rash appearance coincides with defervescence.
6. Koplik spots are the buccal-mucosal analogue: tiny foci of epithelial necrosis with neutrophil infiltrate on an erythematous base, appearing 1 to 2 days before the rash.

[1]

The classic trap: the rash is not the virus damaging skin — it is the immune system clearing infected endothelium. That is why an immunocompromised child with overwhelming measles may have no rash at all, and why fever falls as the rash appears. A child whose fever keeps rising with the rash has a complication — usually secondary bacterial infection.[1]

The most important recent discovery is measles-induced immune amnesia. Measles infection depletes 11 to 73 percent of the pre-existing antibody repertoire — memory B and T lymphocytes carrying immunity to other pathogens are lost, leaving the host susceptible to otitis, pneumonia, diarrhoea and other infections for 2 to 3 years after the acute illness. The mechanism is both the depletion of memory B cells and the replacement of the plasma-cell niche after the lymphopenia of acute infection, so antibody titres to previously encountered pathogens collapse. This is why measles mortality stays elevated for years, not just during the illness.[4][5]

Why SSPE happens: a defective measles variant — mutations especially in the M matrix protein — persists in neurons, is poorly cytolytic, spreads cell-to-cell, and slowly accumulates over years until it triggers a fatal neurodegeneration. The risk is highest when measles is acquired under 2 years of age, presumably because the immature immune system fails to clear the virus and allows persistence. The M protein is needed for viral assembly and budding; when it is mutated, the virus cannot form infectious particles but can still spread directly from cell to cell within the CNS, evading antibody neutralisation.[2]

Etymology for viva gold: rubeola is the Latin diminutive of rubeus, "reddish" — "a little redness". Morbillivirus is from morbus, "disease", as the "little disease" set against Rinderpest, the great cattle plague to which it is closely related. Rinderpest was declared eradicated in 2011; measles, its human cousin, was meant to follow.[1]

The clinical forms — and the atypical ones that bite

Measles is one entity with several clinical phenotypes that depend on the host's prior immunity and age.[1]

[1]

The classic trap: modified measles is still infectious. A recently vaccinated child, an infant with maternal antibody, or a contact given immunoglobulin can have a mild, sparse-rash illness that you write off as a viral exanthem — and they seed the next outbreak. The discriminator is RT-PCR, because IgM may be attenuated; isolate and confirm rather than reassure.[1]

Measles neurological syndromes are a distinct, examinable classification — and the timing of each is the discriminator:[2][9]

• Acute disseminated encephalomyelitis (ADEM, post-measles encephalomyelitis) — demyelinating, perivascular, autoimmune; within 2 to 14 days of the rash; about 1 in 1000 cases; high morbidity.
• Acute measles encephalitis — direct viral invasion in the immunocompromised; fever, seizures, depressed consciousness.
• Measles inclusion-body encephalitis (MIBE) — in the immunocompromised, 1 to 10 months after infection; rapidly progressive, often fatal.
• Subacute sclerosing panencephalitis (SSPE) — a persistent, defective (M-mutant) measles infection of neurons appearing 5 to 15 years after natural measles (earlier and more frequent when measles is acquired under 2); progressive cognitive decline, myoclonus, seizures, decorticate state, uniformly fatal in 1 to 3 years.

[1] [2]

The four phases — incubation, prodrome, exanthem, recovery

Measles has a stereotyped four-phase clinical course. Knowing which phase you are in tells you what to do next.[1][2]

Phase 1 — Incubation (10 to 14 days, range 7 to 21): asymptomatic, but the patient becomes infectious about 4 days before the rash. This silent infectious window is the main reason outbreaks are so hard to contain.[1]

Phase 2 — Prodrome (catarrhal stage, 2 to 4 days): the patient looks and feels unwell. The 3 Cs are the high-yield triad:[1]

• Cough — dry, brassy, persistent (viral tracheobronchitis); often the last symptom to resolve.
• Coryza — sneezing, nasal discharge and obstruction; the child is snotty and congested.
• Conjunctivitis — red, watery, often photophobic; may progress to keratitis, especially with vitamin A deficiency.

[1]

Accompanying features: high fever (often 39 to 40.5 degrees C), malaise, anorexia, myalgia, sometimes mild pharyngitis. Fever often rises in a step-ladder pattern to a peak on the day the rash erupts. Koplik spots — pathognomonic — appear on the buccal mucosa opposite the lower second molars during the late prodrome (1 to 2 days before the rash): tiny (1 to 3 mm) bluish-white "grains of salt" papules on a bright-red erythematous base, fading 1 to 2 days after the rash appears. Koplik spots are diagnostic when present — examiners call them "grains of salt on a red carpet".[1]

Phase 3 — Exanthem (rash stage): a maculopapular, erythematous, blanching, usually non-pruritic rash that becomes confluent. The distribution is cephalocaudal and is itself diagnostic:[1]

• Day 1 — appears behind the ears and at the hairline on the face, neck; spreads to the face and upper neck.
• Day 2 to 3 — spreads down the trunk, becoming confluent on the face.
• Day 3 to 4 — reaches the limbs (including palms and soles); the face begins to clear.

[1]

As the rash appears, fever begins to defervesce over the next 2 to 3 days — a still-rising fever with the rash suggests a complication. A fine desquamation and brownish staining may follow over the next week. Generalised lymphadenopathy and mild splenomegaly are common; the rash may be purpuric in severe disease or thrombocytopenia.[3]

Phase 4 — Recovery: fatigue and cough may persist 1 to 2 weeks. The patient is infectious until 4 days after the rash appears (longer in the immunocompromised — the entire illness).[1]

The mimics — distinguish the exanthems before you commit

An acute febrile illness with a maculopapular rash is not always measles. The distribution, the prodrome, Koplik spots, and the patient's immune and exposure history are the discriminators. Always consider rubella (especially in pregnancy), parvovirus B19, Kawasaki disease, and drug reactions.[3]

[3]

The one-line discriminators to commit to memory: Koplik spots equal measles; postauricular nodes plus Forscheimer spots plus pregnancy concern equal rubella; rash as fever drops equals roseola; slapped cheek equals parvovirus B19; sandpaper plus strawberry tongue equals scarlet fever; five-day fever plus cracked lips plus coronary risk equals Kawasaki.[3]

Everyone forgets: examine the buccal mucosa before the skin in any febrile child with cough, coryza and conjunctivitis. Koplik spots appear before the rash, so the mouth can clinch the diagnosis at the prodromal stage, when isolation and contact tracing are most valuable. In a pregnant woman with a rash, always ask about rubella immunity and parvovirus B19 exposure — both have fetal implications that measles does not.[1]

The bedside round — drive severity and find the complications

Vital signs drive severity and complications. Check temperature, respiratory rate, oxygen saturation, hydration, capillary refill, alertness, and look systematically for the complications.[9]

The targeted bedside examination:[1]

• Buccal mucosa — inspect under bright light opposite the lower molars for Koplik spots (pathognomonic); they may be few and fleeting.
• Conjunctivae and cornea — redness, discharge, photophobia; examine with fluorescein for keratitis or corneal ulcer (the vitamin A deficiency link).
• Ears — pneumatic otoscopy for otitis media (bulging, red, immobile tympanic membrane; the commonest bacterial complication).
• Respiratory — signs of pneumonia (tachypnoea, crackles, bronchial breath sounds, effusion), croup (stridor), and hypoxia.
• Abdomen — dehydration from diarrhoea; hepatosplenomegaly.
• Neurology — irritability, meningism, seizures, depressed consciousness (encephalitis), and — years later — myoclonus and school decline (SSPE).
• Nutrition — weight-for-height, mid-upper-arm circumference, signs of vitamin A deficiency (xerosis, Bitot spots, corneal ulceration).
• Skin — character and distribution of the rash; desquamation; petechiae or purpura.

[1]

Assess for the four lethal complications at every contact: pneumonia, dehydration, encephalitis, and keratitis or blindness.[1]

The tests — clinical in outbreaks, confirmed in sporadic cases

Diagnosis is primarily clinical in an outbreak — typical prodrome with Koplik spots plus cephalocaudal rash — but laboratory confirmation is mandatory for sporadic cases, atypical cases, and public-health notification.[1][2]

First-line laboratory confirmation:[1]

• Measles-specific IgM serology — positive from 1 to 2 days after the rash appears, peaks at 1 to 3 weeks, persists 30 to 60 days. A single positive IgM in someone not recently vaccinated confirms acute measles. False negatives occur in the first 1 to 2 days of rash (repeat at 7 to 10 days); false positives from rheumatoid factor, parvovirus, EBV. IgM may be delayed or absent in modified measles or after immunoglobulin.
• Measles RNA by RT-PCR — throat swab, nasopharyngeal aspirate, or urine; most sensitive in the first 3 to 4 days of the rash; allows genotyping to identify the outbreak source and distinguish wild-type from vaccine-strain measles. PCR is preferred in modified or atypical measles and in the immunocompromised.
• Salivary measles IgM (where available) — non-invasive, useful in children.

[1]

Supporting tests:[1]

• Full blood count — typically leucopenia with lymphopenia (the immune amnesia); sometimes atypical lymphocytes; thrombocytopenia may occur.
• Vitamin A level — in severe or malnourished cases (subclinical deficiency worsens outcomes); do not wait for a level to give vitamin A.
• Chest X-ray if pneumonia is suspected — interstitial infiltrates (viral giant-cell pneumonia), lobar consolidation (secondary bacterial), hilar adenopathy, sometimes pleural effusion.
• CT brain, EEG and CSF for suspected encephalitis — CSF shows lymphocytic pleocytosis and may detect measles antibody; EEG in SSPE shows characteristic periodic complexes with burst-suppression.

[1]

Paired serology — a four-fold rise in measles IgG between acute and convalescent sera (2 to 3 weeks apart) confirms infection when IgM is unobtainable; rarely needed now that PCR is widespread but useful in retrospective or atypical cases.[1]

WHO and CDC case definition (high-yield):[8]

• Suspected case — any person with fever and maculopapular rash AND at least one of cough, coryza, or conjunctivitis.
• Laboratory-confirmed case — suspected case with positive measles IgM (not recently vaccinated), OR measles RNA by RT-PCR, OR a four-fold rise in IgG, OR epidemiologically linked to a laboratory-confirmed case.

[1]

[1]

The first hour — isolate and notify, then resuscitate

The two non-negotiable immediate actions on suspecting measles are to ISOLATE and to NOTIFY.[1][7]

Isolation — airborne precautions: place the patient in a single room, preferably negative-pressure, with FFP3 or N95 respiratory protection for staff — the measles virus aerosolises and lingers for up to two hours. Isolate for at least 4 days after the rash appears (longer in the immunocompromised — the entire duration of illness). Only staff with documented immunity (two documented MMR doses or positive IgG) should enter; susceptible staff should not care for the patient, and if exposed, are excluded from work from day 5 to 21.[7]

Notify public health immediately — measles is statutorily notifiable worldwide, and notification triggers contact tracing and outbreak control. Include the patient's demographics, onset date, rash date, vaccination history, and known contacts. This is not bureaucracy; it is a clinical intervention that prevents further cases.[7]

[1] [7]

Definitive management — supportive, vitamin A, no antiviral

There is no specific antiviral of proven benefit in measles. Management is supportive, with vitamin A to every child, treatment of complications, and rigorous infection control and public-health action.[2][6]

Supportive care:[1]

• Antipyretics and analgesia — paracetamol 10 to 15 mg/kg every 4 to 6 hours (maximum 60 mg/kg/day, 4 g/day in adults), or ibuprofen 5 to 10 mg/kg every 6 to 8 hours for fever, myalgia, headache. Avoid aspirin in children (Reye syndrome).
• Hydration and nutrition — maintain oral intake; IV fluids if dehydrated; nutritional rehabilitation in the malnourished; continue breastfeeding.
• Eye care — protect the cornea in keratitis or xerophthalmia; antibiotic eye ointment; ophthalmology review.
• Cough and respiratory support — humidified oxygen, bronchodilators if wheeze; mechanical ventilation for severe pneumonia or ARDS.

[1]

Vitamin A — give to ALL children with measles (WHO recommendation; reduces mortality roughly 50 to 60 percent in deficient populations and prevents blindness):[6][7]

• Two doses, 24 hours apart:
  • 200,000 IU orally if age 12 months or older.
  • 100,000 IU orally if age 6 to 11 months.
  • 50,000 IU orally if under 6 months.
• A third dose 2 to 4 weeks later in confirmed vitamin A deficiency, xerophthalmia, or persistent malnutrition.

[1]

Vitamin A is thought to work by restoring epithelial integrity, supporting immune function, and reducing the severity of keratitis and diarrhoea. The WHO recommendation is to give it to all children with measles regardless of measured serum levels or national setting, because even subclinical deficiency worsens outcomes and serum levels fall during acute infection. High-dose vitamin A can cause transient headache, vomiting and a bulging fontanelle in infants — usually mild and self-limiting, and far outweighed by the benefit.[6]

Treatment of complications:[1]

• Otitis media — oral amoxicillin 40 to 90 mg/kg/day in 2 to 3 divided doses for 5 to 10 days (or co-amoxiclav if treatment failure), per local guidance.
• Secondary bacterial pneumonia — empirical CAP therapy (ceftriaxone plus azithromycin for severe; amoxicillin or co-amoxiclav for milder disease); cover pneumococcus, H. influenzae, Staphylococcus aureus.
• Viral (giant-cell or Hecht) pneumonia — supportive; oxygen and ventilation as needed. IV ribavirin is sometimes used in severe life-threatening disease, especially in the immunocompromised (off-label, limited evidence; teratogenic — avoid in pregnancy).
• Acute encephalitis — supportive intensive care; control seizures (IV lorazepam 0.1 mg/kg or rectal diazepam 0.5 mg/kg), treat raised intracranial pressure; the evidence for steroids, IVIG and plasmapheresis in ADEM is limited.
• SSPE — no curative treatment; isoprinosine (inosine pranobex) and intraventricular interferon-alpha may slow progression in some; ultimately symptom control and supportive care.

[1] [7]

Hospitalisation criteria: any complication (pneumonia, dehydration, encephalitis, severe keratitis, secondary bacterial infection), infants, immunocompromise, malnutrition, pregnancy, or unsafe social situation. Step down once the patient is clinically improving, afebrile, hydrated, tolerating oral intake and oxygen-independent, with isolation discontinued 4 days after the rash appeared (longer if immunocompromised).[1]

The subtypes and scenarios that change the plan

[1] [2]

The complications — pneumonia is the killer, SSPE is the trap

Complications are common and severe, especially in the under-fives, adults over 20, the malnourished, the immunocompromised, and pregnant women.[9]

[2] [9]

Pneumonia deserves its own sentence because it is the commonest cause of death. It can be primary viral giant-cell (Hecht) pneumonia — interstitial infiltrates with giant cells on biopsy — or secondary bacterial pneumonia, most often pneumococcal, Haemophilus influenzae type b, or Staphylococcus aureus. In practice the two are often indistinguishable clinically, and empirical antibiotics are indicated for any pneumonia in measles. Hypoxia, respiratory distress, and persistent fever after the rash should be treated as pneumonia until proven otherwise.[9]

Neurological complications are the other high-yield cluster. Acute measles encephalitis occurs in about 1 in 1000 cases, with mortality of 15 percent and sequelae in 25 to 40 percent of survivors. ADEM is an immune-mediated demyelination 2 to 14 days after the rash. MIBE is a usually fatal encephalitis in the immunocompromised, 1 to 10 months after infection. SSPE is the late, fatal complication every examiner expects — progressive cognitive decline, behavioural change, myoclonus, seizures, EEG periodic complexes with burst-suppression, and raised measles antibody in CSF and serum; uniformly fatal in 1 to 3 years, and the risk is highest when measles is acquired under 2.[2]

How measles patients come to harm — the preventable list:[1][9]

• Death from pneumonia (viral or secondary bacterial) missed because a rising fever with the rash was attributed to the illness rather than a complication.
• Blindness from keratitis in a vitamin-A-deficient child who was not given vitamin A.
• A nosocomial outbreak seeded by a patient in a waiting room on droplet precautions instead of airborne.
• A missed diagnosis written as drug rash or dengue because the buccal mucosa was never examined.
• SSPE missed for years in a child whose school decline and myoclonus were attributed to behaviour.
• Live MMR given in pregnancy or immunocompromise — HNIG was the correct call.
• Contacts not vaccinated within the 72-hour (MMR) or 6-day (HNIG) windows.[1][9]

Prognosis and disposition

Most uncomplicated cases recover within 7 to 10 days of the rash. Case fatality in well-nourished, developed settings is 1 to 3 in 1000, rising to 5 to 10 percent (and higher in refugee or displaced populations) in malnutrition and the immunocompromised. Death is most often from pneumonia (viral or secondary bacterial) or encephalitis.[9]

Poor-prognostic factors: age under 5 or over 20, malnutrition (especially vitamin A deficiency), immunocompromise, pregnancy, no prior vaccination, secondary bacterial infection, delayed vitamin A, and crowded or low-resource settings. SSPE is uniformly fatal 1 to 3 years from onset. Lifelong immunity follows natural measles (re-infection is rare); two-dose MMR gives over 97 percent protection.[2][7]

Disposition is driven by complication severity: home with a safety-net for uncomplicated cases; hospital for any complication, infants, immunocompromise, malnutrition, pregnancy, or poor social situation; ICU for severe pneumonia, ARDS, encephalitis, or shock. Discontinue isolation 4 days after the rash appeared (longer if immunocompromised).[1]

Special populations — pregnancy, the immunocompromised, the infant

Children — weight-based dosing for paracetamol, vitamin A and antibiotics; infants at higher risk. MMR at 9 months in India's Universal Immunisation Programme (6 months in an outbreak, then repeated), second dose at 15 to 18 months. Maternal antibody wanes by 6 to 9 months, opening a susceptibility gap; in an outbreak, infants as young as 6 months may receive MMR, but this dose does not count toward routine immunity and must be repeated.[7]

Malnutrition and vitamin A deficiency — severe disease, keratitis, blindness, high mortality; vitamin A is essential (two doses, third in deficiency) plus nutritional rehabilitation. Measles and malnutrition form a vicious cycle: measles causes anorexia and diarrhoea, worsening malnutrition; malnutrition impairs immunity, worsening measles.[6]

Immunocompromised (HIV, transplant, chemotherapy, primary immunodeficiency) — severe or atypical disease (no rash, giant-cell pneumonia, encephalitis, MIBE); live MMR is CONTRAINDICATED; HNIG within 6 days of exposure; consider IV ribavirin for severe disease. Some HIV-positive children with preserved CD4 counts may receive MMR under specialist direction.[2]

Pregnant women — higher risk of severe measles, miscarriage, preterm labour, low birthweight; NOT teratogenic (unlike rubella); live MMR contraindicated in pregnancy (give postpartum); HNIG within 6 days of exposure. The absence of teratogenicity is a common exam point: rubella causes congenital rubella syndrome, measles does not.[2]

Newborn of a mother with measles — HNIG; supportive care; observe for severe disease; breastfeeding encouraged. Congenital measles is not a defined syndrome (unlike rubella); postnatal exposure from the mother or close contacts is the more common route.[2]

Tuberculosis co-infection — measles transiently suppresses cell-mediated immunity, may reactivate TB, and causes tuberculin skin test (TST) anergy for 4 to 6 weeks; live MMR can theoretically interfere with BCG or TST — separate MMR from BCG or TST by about 4 weeks where feasible.[2]

The evidence that changed practice

The headline evidence an examiner expects:[1]

• MMR does NOT cause autism. The 1998 Wakefield Lancet paper was fully retracted in 2010; the large cohort study by Hviid et al. 2019 in 657,461 Danish children (Annals of Internal Medicine) found no increased risk of autism with MMR, even in children with a family history of autism or other susceptibility factors. The adjusted hazard ratio was 0.93 (95 percent CI 0.85 to 1.02).[10]
• Vitamin A reduces measles mortality. Hussey and Klein's 1990 NEJM randomised trial and subsequent Cochrane reviews established two-dose vitamin A as the WHO standard, with reduced mortality and pneumonia-specific mortality in children with severe measles.[6]
• Immune amnesia. Mina et al. (2015, Science) showed population-level rises in non-measles infectious disease mortality for 2 to 3 years after measles epidemics in England and Wales, the USA and Denmark. Mina et al. (2019, Science) demonstrated that measles depletes 11 to 73 percent of the pre-existing antibody repertoire, mechanistically explaining immune amnesia.[4][5]
• Vaccine effectiveness — one dose about 93 percent, two doses about 97 percent; herd immunity needs about 92 to 95 percent coverage. The Disneyland 2014 to 2015 outbreak and the UK loss of elimination in 2018 show how small coverage gaps cause large outbreaks.[7]

[1]

Regional guideline differences:[1]

Post-exposure prophylaxis decision algorithm: for a susceptible contact of a measles case, offer MMR vaccine within 72 hours of first exposure if there are no contraindications to live vaccine. For contacts in whom live vaccine is contraindicated — pregnant women, severely immunocompromised patients, and infants under 6 months — give human normal immunoglobulin (HNIG) 0.5 mL/kg IM (maximum 15 mL) within 6 days of first exposure. HNIG may attenuate disease but does not always prevent it; the patient should still be monitored.[1]

The mantra, and the mnemonic

[1] [3]

The mantra: 3 Cs and Koplik before the rash, head-to-toe as the fever falls, vitamin A to every child, airborne isolation, MMR for the contacts.[1][6]

Ward-round test — three stems, thirty seconds each

Stem 1 — the child from the top of the topic (answer)

The four-year-old with cough, coryza, conjunctivitis and Koplik spots, no rash yet, unimmunised. What do you do in the next hour? Model: This is measles prodrome — Koplik spots are pathognomonic. Isolate immediately with airborne precautions (single negative-pressure room, FFP3 or N95 for staff), notify public health the same hour, and confirm with RT-PCR on throat or urine (IgM may still be negative before the rash). Give vitamin A, two doses 24 hours apart (200,000 IU). Trace contacts: offer MMR within 72 hours to susceptible contacts, and HNIG within 6 days for pregnant women, the immunocompromised and infants under 6 months. Isolate until 4 days after the rash appears. Watch for pneumonia — the commonest cause of death.[1][7]

Stem 2 — the immunocompromised adult with pneumonia and no rash (answer)

A 35-year-old with HIV and a low CD4 count has interstitial pneumonia and is hypoxic, with no rash. A relative had measles two weeks ago. What is going on, and why is there no rash? Model: This is measles giant-cell (Hecht) pneumonia in the immunocompromised. There is no rash because the rash is a cell-mediated (type IV) immune attack on infected endothelium — and this patient's cell-mediated immunity cannot mount it. Confirm with RT-PCR on throat or urine (IgM may be unreliable). Treat supportively with oxygen and ventilation; consider IV ribavirin for severe disease. Give HNIG if seen within 6 days of exposure — and remember that live MMR is contraindicated in this patient for life. MIBE is the later neurological threat at 1 to 10 months.[2]

Stem 3 — the school-decline child years later (answer)

A nine-year-old has been deteriorating at school for six months, with myoclonic jerks and progressive loss of motor skills. He had measles at 18 months. What is this, and what is the prognosis? Model: This is subacute sclerosing panencephalitis (SSPE) — a persistent, defective (M-matrix-mutant) measles infection of neurons appearing 5 to 15 years after natural measles, with higher risk when measles was acquired under 2. Confirm with EEG (periodic complexes with burst-suppression) and raised measles antibody in CSF and serum. There is no curative treatment; isoprinosine (inosine pranobex) and intraventricular interferon-alpha may slow progression in some. The prognosis is uniformly fatal in 1 to 3 years. The lesson is upstream — two-dose MMR prevents the measles that prevents SSPE.[2]

References

1. [1]Rota PA, Moss WJ, Takeda M, de Swart RL, Thompson KM, Goodson JL. Measles Nat Rev Dis Primers, 2016.PMID 27411684
2. [2]Moss WJ, Griffin DE. Measles Lancet, 2012.PMID 21855993
3. [3]Keighley CL, Saunderson RB, Kok J. Viral exanthems Curr Opin Infect Dis, 2015.PMID 25706914
4. [4]Mina MJ, Metcalf CJ, de Swart RL, Osterhaus AD, Grenfell BT. Long-term measles-induced immunomodulation increases overall childhood infectious disease mortality Science, 2015.PMID 25954009
5. [5]Mina MJ, Kula T, Leng Y, et al. Measles virus infection diminishes preexisting antibodies that offer protection from other pathogens Science, 2019.PMID 31672891
6. [6]Hussey GD, Klein M. A randomized, controlled trial of vitamin A in children with severe measles N Engl J Med, 1990.PMID 2194128
7. [7]World Health Organization. Measles vaccines: WHO position paper, April 2017 - Recommendations Vaccine, 2019.PMID 28760612
8. [8]Perry RT, Gacic-Dobo M, Dabbagh A, Mulders MN, Strebel PM, Okwo-Bele JM, Rota PA, Goodson JL. Progress toward regional measles elimination - worldwide, 2000-2014 MMWR Morb Mortal Wkly Rep, 2015.PMID 26562349
9. [9]Perry RT, Halsey NA. The clinical significance of measles: a review J Infect Dis, 2004.PMID 15106083
10. [10]Hviid A, Hansen JV, Frisch M, Melbye M. Measles, Mumps, Rubella Vaccination and Autism: A Nationwide Cohort Study Ann Intern Med, 2019.PMID 30831578