SID 10: Measles

1. Why measles has re-emerged as a public health concern in Canada

Measles used to be eliminated

  • Canada eliminated measles ~25 years ago

  • Cases dropped 99% between 1970–2024 due to vaccination programs.

    SID 10_ Measles

But recently it returned

The Pan American Health Organization (PAHO) removed Canada's measles-free certification because:

  • Canada failed to stop an outbreak for 12 consecutive months.

    SID 10_ Measles

Main reasons for resurgence

1⃣ Declining vaccination rates

  • More people are unvaccinated or undervaccinated

  • This weakens herd immunity

2⃣ Increased global travel

  • Measles is still common in many countries

  • Travelers can import measles cases into Canada

Why this matters

Measles spreads extremely easily:

  • R₀ = 12–18

  • One infected person infects 12–18 others

  • ~10× more contagious than COVID-19 or influenza.

    SID 10_ Measles

✔ Because of this high transmissibility, even small drops in vaccination coverage can trigger outbreaks.

2. Signs and symptoms of measles

Classic presentation

The hallmark is:

Fever + the “3 Cs”

1⃣ Conjunctivitis

  • Red, inflamed eyes

2⃣ Coryza

  • Runny nose

3⃣ Cough

Plus:

  • High fever

  • Sometimes diarrhea.

    SID 10_ Measles

Characteristic rash findings

There are two important rash features:

1⃣ Koplik spots (ENANTHEM)

  • Small white lesions on the oral mucosa

  • Often appear before the skin rash

2⃣ Skin rash (EXANTHEM)

  • Erythematous macules and papules

  • NOT itchy

  • Red/pink/purple lesions that may appear darker than surrounding skin.

    SID 10_ Measles

Disease course

Typical timeline:

  • Rash lasts: ~6–7 days

  • Symptoms improve ~2 days after rash appears

  • Total illness duration ≈ 2 weeks

After infection:

➡ Lifelong immunity to measles.

SID 10_ Measles

3. Complications of measles infection

Measles is not just a rash illness — it can be severe.

Major complications

1⃣ Pneumonia

  • Most common cause of death

2⃣ Encephalitis

  • Brain inflammation

  • Can cause permanent neurologic damage

3⃣ Subacute Sclerosing Panencephalitis (SSPE)

  • Rare but fatal late complication

  • Occurs years after infection

4⃣ Death.

SID 10_ Measles

Pregnancy complications (very testable)

Pregnant patients are 10× more likely to develop measles if susceptible.

Possible maternal complications:

  • Maternal interstitial pneumonitis

  • Hepatitis

  • 10× higher mortality risk.

    SID 10_ Measles

Fetal / neonatal complications

If infection occurs during pregnancy:

Fetal risks:

  • Spontaneous abortion

  • Fetal growth restriction

  • Preterm birth

If infection occurs within 14 days of delivery:

Neonate may develop:

  • Blindness

  • Deafness

  • Encephalitis

  • Death.

    SID 10_ Measles

4. Treatment of measles

Important exam concept:

⚠ There is NO antiviral treatment for measles.

Treatment is supportive care.

Supportive treatments

1⃣ Antipyretics

  • Acetaminophen 15 mg/kg PO q6h PRN
    OR

  • Ibuprofen 10 mg/kg PO q8h PRN

2⃣ Fluids

3⃣ Rest.

SID 10_ Measles

Special population treatment

Pregnancy exposure

If a susceptible pregnant person is exposed:

➡ IV Immunoglobulin (IVIg) within 6 days of exposure.

Purpose:

  • Passive antibodies

  • Prevent infection or reduce severity.

    SID 10_ Measles

5. Criteria for high-dose Vitamin A treatment

WHO recommendation

All children with measles should receive:

➡ Two doses of Vitamin A 24 hours apart

Reason:

  • Reduces complications and mortality

But this evidence comes from countries with high vitamin A deficiency.

SID 10_ Measles

Canadian recommendations (important)

In Canada, vitamin A deficiency is rare.

So Vitamin A is NOT routinely used for all cases.

Give Vitamin A only if:

1⃣ Confirmed measles + hospitalization

OR

2⃣ Immunocompromised children in the community.

SID 10_ Measles

Dosing

Age

Dose

<6 months

50,000 IU PO daily × 2 days

6–11 months

100,000 IU PO daily × 2 days

≥12 months

200,000 IU PO daily × 2 days

NOT recommended

  • Children diagnosed with measles in the community without risk factors.

Reason:

  • Little evidence of benefit in high-income countries with low vitamin A deficiency.

    SID 10_ Measles

6. Prevention of measles infection and spread

Infection control

Patients should:

  • Avoid others until ≥4 days after rash onset

  • Practice hand hygiene

  • Wear high-quality masks (e.g., N95)

  • Clean contaminated surfaces

Important because:

  • Virus survives in air/surfaces for up to 2 hours.

    SID 10_ Measles

Vaccination (most important prevention)

MMR vaccine (Measles, Mumps, Rubella)

Type:

  • Live attenuated vaccine

Schedule:

  • First dose: ≥12 months

  • Second dose: booster

Effectiveness:

  • 95% seroconversion after 1st dose

  • ~100% after 2nd dose.

    SID 10_ Measles

Important concept:

  • Infants <12 months do not respond well because maternal antibodies neutralize the vaccine.

⭐ SUPER HIGH-YIELD EXAM SUMMARY

If your prof asks quick MCQs, remember:

Measles basics

  • Paramyxovirus

  • R₀ = 12–18 (VERY contagious)

Classic symptoms

  • Fever + 3 Cs

    • Conjunctivitis

    • Coryza

    • Cough

  • Koplik spots

  • Maculopapular rash

Complications

  • Pneumonia

  • Encephalitis

  • SSPE

  • Death

Treatment

  • No antivirals

  • Supportive care

Vitamin A
Give only if:

  • Hospitalized measles
    OR

  • Immunocompromised child

Prevention

  • MMR vaccine (2 doses)