Measles
Exam Tips
- Classic triad for exams: cough, coryza, conjunctivitis plus high fever and descending maculopapular rash.
- Koplik spots are highly suggestive and may appear before the rash.
- Infectious period is tested frequently: from about 4 days before to 4 days after rash onset.
- Always state public health action: measles is notifiable and suspected cases require same-day HPT notification with lab confirmation arranged in parallel.
- In vaccinated or immunocompromised patients, presentation may be atypical (mild or absent rash), so epidemiology and exposure history become crucial.
- See typical rash progression images in DermNet measles resources (useful visual differential practice).
- Do not prescribe aspirin to children under 16 years (Reye syndrome risk).
Definition
Measles is an acute, highly contagious viral illness caused by a morbillivirus (paramyxovirus family) and spread by respiratory droplets and airborne particles. After an incubation of about 7-21 days (typically around 10), a prodrome of fever, cough, coryza and conjunctivitis is followed by a cephalocaudal maculopapular rash; infectivity runs from about 4 days before rash onset to 4 days after.
Pathophysiology
The virus enters via the respiratory epithelium, replicates locally, and spreads through lymphatics and blood (primary then secondary viraemia) to skin, respiratory tract and other organs. The rash reflects host cell-mediated immune response to infected endothelial/epithelial tissues rather than direct viral cytotoxicity alone. Measles also induces prolonged immune dysfunction (immune amnesia), reducing pre-existing immune memory and increasing susceptibility to secondary bacterial and viral infections for weeks to months (and potentially longer). CNS injury in encephalitis is usually post-infectious inflammation or direct viral involvement, while SSPE is a delayed persistent CNS infection years after initial measles.
Risk Factors
- No or incomplete MMR vaccination
- Close contact exposure (same room for 15 minutes or more, or face-to-face contact)
- Residence in or travel to areas with active measles transmission
- Young adults with incomplete childhood immunisation
- Immunocompromise (higher risk of severe/prolonged disease and atypical presentation)
- Infancy (especially under 1 year)
- Pregnancy
- Malnutrition, including vitamin A deficiency
Clinical Features
Symptoms
- High fever (often 39 degrees C or above)
- Malaise and anorexia in prodrome
- Cough
- Coryzal symptoms (rhinorrhoea)
- Conjunctivitis/photophobia
- Rash starting on face/behind ears then spreading down trunk and limbs over 3-4 days
Signs
- Erythematous maculopapular rash that may become confluent
- Koplik spots on buccal mucosa (red lesions with white-blue centres) near rash onset
- Pyrexia peaking around rash appearance then gradually settling
- Cervical lymphadenopathy may be present
- In immunosuppressed patients, classical rash may be absent
Investigations
Management
Lifestyle Modifications
- Isolate: avoid school/work and vulnerable contacts until 4 days after rash onset
- Hydration, rest, and fever comfort measures
- Safety-net: urgent review for breathing difficulty, reduced oral intake/urine output, confusion, seizures, persistent fever, or non-blanching rash
- Public health actions: contact tracing and exposure risk assessment through HPT
- Check and update MMR status after recovery for patient/household where appropriate
Pharmacological Treatment
Antipyretic/analgesic
- Paracetamol oral: adults 500 mg-1 g every 4-6 hours when required (max 4 g/day)
- Paracetamol oral: 6-11 years 250-500 mg every 4-6 hours (max 4 doses/24 hours)
- Paracetamol oral: 12-15 years 500-750 mg every 4-6 hours (max 4 doses/24 hours)
Use weight/age-appropriate formulations in children; avoid exceeding total daily dose; counsel carers to avoid duplicate paracetamol-containing products.
NSAID antipyretic (if appropriate)
- Ibuprofen oral: 3 months-11 years 5-10 mg/kg per dose 3 times daily (max 30 mg/kg/day)
- Ibuprofen oral: 12-17 years 200-400 mg up to 3 times daily
Avoid in dehydration, significant renal impairment, active GI ulceration, and NSAID-sensitive asthma; give with/after food if tolerated.
Antibiotics for secondary bacterial infection only
- Amoxicillin oral (example for community-acquired bacterial pneumonia): adults 500 mg three times daily for 5 days
- Clarithromycin oral if penicillin allergy (example): adults 500 mg twice daily for 5 days
Do not use antibiotics for uncomplicated viral measles; choose agent/duration by site and severity of confirmed bacterial complication and local antimicrobial guidance.
Post-exposure prevention in selected contacts
- MMR vaccine 0.5 mL IM or deep SC (catch-up in susceptible contacts when indicated)
- Human normal immunoglobulin for high-risk exposed contacts (pregnant, immunocompromised, certain infants) as directed by specialist/HPT protocols
Selection and timing are risk-stratified through HPT; MMR is contraindicated in severe immunosuppression and pregnancy; defer live vaccine after immunoglobulin for the recommended interval.
Complications
- Otitis media
- Laryngotracheobronchitis and pneumonitis
- Secondary bacterial pneumonia
- Diarrhoea with dehydration
- Stomatitis
- Febrile convulsions
- Acute encephalitis
- Subacute sclerosing panencephalitis (late, rare, fatal)
- Keratoconjunctivitis and vision loss (risk increased with vitamin A deficiency)
- Severe/prolonged disease in immunocompromised patients
- Pregnancy complications: miscarriage, prematurity, stillbirth, maternal morbidity/mortality
Prognosis
Most immunocompetent children recover fully with supportive care over about a week after rash onset, but complications occur in a notable minority and are more common/severe in infants, adults, immunocompromised people, and during pregnancy. Mortality is low in high-income settings but rises where nutrition, vaccination coverage, or access to care are poor; in the UK, deaths are uncommon and predominantly in unvaccinated individuals.
Sources & References
✅NICE Guidelines(1)
- Measles[overview]