Measles: A Primer for Medical Students 🦠

 Measles cases in the US are now over 1,000 cases across 30 states. 3 people have died in this outbreak and 130 have been hospitalised. And it is not slowing down. 

There is currently much discussion about measles worldwide, and most of you will have never seen a case of it  - but that certainly doesn't mean you can ignore it. Do so at your peril! 

Measles is a highly contagious viral disease that can cause severe complications and, in some cases, death - particularly in young children, immunocompromised individuals, and unvaccinated populations. Although now rare in Australia due to successful vaccination programs, measles remains a global health threat, with imported cases continuing to cause small outbreaks here.

🔬 The Virus Behind Measles

The measles virus (MeV) is a single-stranded, negative-sense RNA virus from the Paramyxoviridae family and genus Morbillivirus.

Structure: Enveloped virus with a surface covered in hemagglutinin (H) and fusion (F) glycoproteins.

Target Cells: Primarily infects respiratory epithelial cells and then spreads via the bloodstream to other organs.

Immune Impact: Measles induces transient immunosuppression by depleting memory B and T cells, leaving patients vulnerable to secondary bacterial infections for weeks to months post-infection.

🦠 Infectiousness: One of the World’s Most Contagious Viruses

Measles has a basic reproduction number (R₀) of 12–18, making it more contagious than influenza, mumps, or COVID-19 (original strain).

The virus is transmitted through respiratory droplets and aerosolised particles, which can linger in the air for up to 2 hours after an infectious person has left the area.

90% of susceptible individuals exposed to the virus will become infected.

⚠️ How It Spreads:

Direct contact with infectious secretions (e.g., coughing, sneezing).

Airborne transmission in shared indoor spaces.

Contaminated surfaces, though this is less common than airborne spread.

👨‍⚕️ Clinical Presentation:

Symptoms typically appear 7–18 days post-exposure (average 10–14 days) and include:

Prodromal phase: High fever, cough, coryza, conjunctivitis (the 3 Cs) + malaise.

Pathognomonic sign: Koplik spots – small white spots with a bluish centre on the buccal mucosa.

Rash phase: A maculopapular rash starting on the face, then spreading downward. It blanches initially, becomes non-blanching over time, and lasts 4–7 days.

Other symptoms: Diarrhoea (common in infants), otitis media, and generalised lymphadenopathy.

🚨 Complications:

Measles is not a benign childhood illness—up to 30% of cases result in complications:

Respiratory: 

Pneumonia (the leading cause of measles-related deaths).

Neurological:

Acute measles encephalitis (~1 in 1000 cases).

Post-infectious encephalomyelitis (PIE) – an autoimmune phenomenon occurring weeks after the acute illness.

Subacute sclerosing panencephalitis (SSPE) – a rare, fatal, progressive neurological condition developing years later.

Gastrointestinal: 

Diarrhoea and dehydration, particularly in infants.

🧬 Measles Cases in Australia (2019–2024):

Despite Australia’s strong immunisation program, sporadic outbreaks persist due to cases imported from overseas.

The graph below illustrates the pattern of measles cases over the past five years:

📊 What Happened in 2019?

In 2019, 286 cases of measles were reported in Australia—nearly triple the 2018 numbers.

This spike was largely driven by imported cases from countries with large outbreaks, such as the Philippines and parts of Europe.

The numbers plummeted in 2020 and 2021 due to COVID-19-related travel restrictions but have rebounded since international travel resumed.

💉 Prevention: Vaccination is Critical

The MMR vaccine (measles-mumps-rubella) provides long-term immunity after two doses.

It is administered in Australia under the National Immunisation Program (NIP):

12 months: MMR vaccine

18 months: MMRV vaccine (measles-mumps-rubella-varicella)

Catch-up vaccination is free for individuals born after 1966 without documented immunity.

Travellers heading overseas should ensure they are fully vaccinated before departure, as outbreaks are still common globally.

Key Takeaways

✅ Be vigilant when encountering fever and rash—always consider measles, especially in returning travellers or unvaccinated individuals.

✅ Isolate suspected cases immediately to prevent airborne transmission.

✅ Check vaccination status—one of the most reliable ways to protect communities.

✅ Educate patients on the importance of measles immunisation, particularly when discussing travel plans.

🚑 Suspected Measles? What Clinicians Should Do:

Isolate Immediately 🚫

• Measles is highly contagious via airborne transmission.
• Isolate the patient in a room with negative pressure ventilation if available, or a single room with the door closed.
• Provide a surgical mask to the patient to minimise respiratory droplet spread.

Take a Detailed History 📋

• Travel history: Any international travel in the past 18–21 days, particularly to areas with active outbreaks.
• Contact history: Any known contact with confirmed or suspected measles cases.
• Vaccination status: Confirm whether the patient has received two documented doses of the MMR vaccine.

Test to Confirm the Diagnosis 🧪

• Nasopharyngeal or throat swab for measles RNA PCR.
• Urine sample for PCR testing (often positive even after the rash appears).
• Serology (IgM and IgG) – note that IgM may not be positive immediately, so testing should be repeated if clinical suspicion remains high.

Notify Public Health Authorities 📞

• Measles is a notifiable disease in Australia—immediate notification is required to allow for contact tracing and outbreak control.
• Contact your state or territory public health unit without waiting for lab confirmation if clinical suspicion is high.

Provide Supportive Care & Patient Education 💊

• No specific antiviral treatment exists for measles—care is supportive with attention to hydration, fever management, and secondary infection prevention.
• Advise the patient to remain isolated until at least 4 days after rash onset.
• Household and close contacts should be assessed for immunity.
• Post-exposure prophylaxis: MMR vaccine if administered within 72 hours of exposure or immunoglobulin (IG) within 6 days for high-risk individuals.

📢 Public Health Follow-Up

• Public health authorities will conduct contact tracing and community notifications if necessary.
• Healthcare workers exposed without documented immunity should be excluded from work for 14 days post-exposure.

🧠 Remember: Measles is preventable but unforgiving. Immediate action upon suspicion can prevent community transmission and save lives.

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