Measles… its backkkk (again)

In the past year, there’s been a growing concern about the rising number of measles cases globally, including in Canada. This resurgence of measles cases in major centers has sparked worry. But is it something we should truly be alarmed about? How concerned should we be?

We’re going to do a deep dive refresher so this is easily accessible on your radar as we get into another school and viral season.

Objectives:

• Provide an overview of the current state of measles in Canada and discuss why it’s concerning.
• Highlight key signs of measles in the Emergency Department and discuss who should be tested.
• Emphasize the importance of vaccinations and how to address vaccine hesitancy.
• Review Public Health and Infectious Disease recommendations for managing measles and post-exposure prophylaxis.

A Brief History

• Measles has been and still is one of the deadliest infectious diseases in the world
• Prior to vaccines:
  • Epidemics occurred every 2-3 years
  • An estimated 2 million deaths per year are attributed to measles
• Vaccines were first introduced in the 1960s and have been the single leading cause of decreased rates of prevalence and death in Canada and around the world
• Canada was able to achieve “measles elimination status” in 1998 meaning >12 months of absence in endemic transmission

Current Climate in Canada

• Over the last several years, the prevalence of measles is relatively low average of approximately 10 cases a year mostly from travel
• In the first 6 months of 2024, there have been 23 cases
  • Comparatively 2.3 times the previous annual average in just half the time
• But why should we be so concerned about spikes in cases?

A Case Study: Quebec (2011)

• In 2011, Quebec suffered one of the largest measles outbreaks in North America
• 21 cases were imported into the Maurice region which led to a subsequent 750 positive cases due to endemic spread
• One case was a young man who returned from a holiday in the Caribbean
  • Due to his role working in a high school and being unknowingly infected while traveling through an airport, he was the index case responsible for causing 678 subsequent cases due to sustained transmission

Transmissibility

• Measles is one of the most infectious diseases in the world
• Attack rate = 90%
• R0 value = 17
  • Compared to COVID-19 (2.5), Ebola (2), smallpox (7)

Clinical Presentation

• Key features to watch out for
  • Fever >38.3 C
  • 3C’s – cough, coryza, conjunctivitis
  • Generalized maculopapular rash
• Stages of infection
  • Incubation
    • 10-14 days from exposure to first symptoms
    • Viral entry via mucous membranes
    • Viral replication in lymphatic tissue
    • Viremia
  • Prodrome
    • Fever, malaise, anorexia
    • Koplik spots
    • 3Cs – cough, coryza, conjunctivitis
  • Exanthem
    • 2-4 days after prodrome, lasts 6-7 days
    • “Morbilliform” – maculopapular rash
      • Typically starts in the face and spreads down but not in all cases
    • Associated lymphadenopathy, fever, respiratory symptoms
  • Recovery
    • Begins 48 hours after rash
    • Recovery after 7-10 days
    • Persistent cough 7-14 days after resolution
    • Fever beyond day 3-4 suggests potential for complications
  • Most infectious period for 4 days before appearance of rash to 4 days after rash

Diagnosis

• When to initiate testing: The Ottawa Hospital algorithm + ID recommendations for testing if below 3 criteria are met
  • Compatible clinical syndrome
    • Fever 38.3 °C+
    • At least 1/3 cough, coryza, conjunctivitis
    • Generalized maculopapular rash
  • Susceptible patient
    • Unvaccinated/partially vaccinated
    • Immunocompromised
  • Epidemiologic link
    • Recent travel within the last 2 weeks
    • Known contact with measles case
    • Residing in an area where measles has recently been identified
  • Tests to send
    • PCR – nasopharyngeal swab
    • PCR – throat swab
    • PCR – urine
    • Serology – IgG/IgM
  • Laboratory diagnosis
    • Positive serologic for IgM 
    • Significant rise in IgG
    • Positive measles virus culture
    • Positive measles viral RNA
  • Case definition
    • Confirmed Case – clinical symptoms plus:
      • Measles virus isolated from sample
      • Detection of viral RNA via PCR
      • Measles IgG seroconversion or rise >4x
      • Measles IgM detection with recent contact or travel
      • Known epidemiological link
    • Probable Case – clinical symptoms plus:
      • Measles IgM detection without recent contact or travel
      • Recent travel to area with known measles activity

Complications

• The reason measles is dangerous is more than just how easily it is transmitted, but also how prevalent complications are and how deadly it can be
• Groups at risk
  • Pregnant women
  • Immunocompromised (cancer, HIV, immunosuppressive medications)
  • Young children
• Common complications
  • Acute otitis media
  • Gastrointestinal inflammation – gastroenteritis, appendicitis, lymphadenitis
  • Superimposed pulmonary infection – most common cause of death worldwide at 6%
• Dangerous complications – concern for neurologic complication and sequelae
  • Encephalitis – morbidity 25%, mortality 15%
  • Acute disseminated encephalomyelitis (ADEM) – mortality 10-20%
  • Subacute sclerosing panencephalitis (SSPE)
    • 7-10 years post infection, progressive and non-curable

Vaccinations are key to prevention

• Measles vaccine is one of the most effective vaccines we have
• Efficacy after a single dose is 85% and goes up to 95% after second
• In Canada, all measles vaccines are combination as MMR or MMRV and given as per Ontario vaccination schedule
  • Dose 1 – 12 months
  • Dose 2 – 4-6 years

Children are not fully immunized for measles until the age of 4-6

• Due to the high transmissibility of measles, a population vaccination rate of 95% is required for herd immunity
• Contraindications to vaccinations – MMR is a live attenuated vaccine
  • Pregnancy
  • Severe immunocompromise

The Story of Vaccine Safety

• Unfortunately, vaccination rates in Canada are at an all time low due to COVID decreasing access to primary care and vaccine hesitancy
• The side effects of the measles vaccine are minor and outweigh the risk of measles disease and complications itself
• Potential side effects
  • Febrile reaction
  • Local discomfort
  • Anaphylactoid
  • Anaphylaxis – to vaccine components, not vaccine itself

The Statistics

Complication rates in approximately 100 children <5 years who receive the vaccine versus contract measles infection

Management

• Isolation
  • Suspected – while labs pending
  • Positive – 9 days total (4 days prior to, 4 days after rash)
  • Immunocompromised – wild symptomatic
• Supportive care
  • Fluids
  • Antipyretics
  • Manage complications
• Vitamin A
  • Pathophysiology
    • Measles can precipitate vitamin A deficiency
    • Vitamin A deficiency associated with adverse effects
    • Delayed recovery, morality from complications, morbidity from blindness
  • Recommendations
    • WHO – 2-day course for all confirmed cases
    • CDC – 2 day course for severe cases, hospitalization, or complications
  • Evidence to decrease mortality and morbidity in low resource settings (higher rates of baseline Vit A deficiency) or severe infections
  • Bottom line
    • Following CDC recommendations in Canada is likely appropriate however vitamin A is a low-risk treatment option
  • Ribavirin
    • Theoretical benefit in severe cases

Post-Exposure Prophylaxis

• Indication
  • Measles exposure
  • Susceptible patient
• Susceptible patient
  • Children <12 months
  • Incomplete vaccinations
  • Immunocompromised
  • Severe immunodeficiency
  • BMT recipient
  • ALL treatment
  • Consider for other immunocompromised states

• Administration
  • Within 72 hours – MMR vaccine
  • Within 6 days – IVIG
  • Pregnant – IVIG
  • Infants <12 mo – IMIG
• If IVIG – will still need MMR in the future

Take Home Points

• Measles is highly contagious, and we need to be aware of potential public health implications
• Think about measles in patients with fever, rash, and symptoms of the 3C’s
• Testing is indicated in patients who have clinical symptoms, possible links, and are susceptible
• Management is supportive but consider the complications, indications for admission, vitamin A
• Vaccination is the end goal, and we should educate patients where possible