Overview
Highly contagious viral disease causing fever, rash, and respiratory symptoms. One of the most infectious pathogens known to science (R0 = 12–18).
Symptoms
Symptoms | Frequency | Severity | Onset |
|---|---|---|---|
| Koplik spots | 70% | Mild | Early |
| Conjunctivitis | 92% | Mild | Early |
| Cough | 95% | Mild | Early |
| High fever | 98% | Severe | Early |
| Malaise | 85% | Mild | Early |
| Rhinorrhea | 90% | Mild | Early |
| Headache | 50% | Mild | Early |
| Irritability | 60% | Mild | Early |
| Excessive tearing | 60% | Mild | Early |
| Loss of appetite | 70% | Mild | Early |
| Photophobia | 50% | Mild | Early |
| Myalgia | 35% | Mild | Early |
| Sore throat | 40% | Mild | Early |
| Maculopapular rash | 99% | Mild | Peak |
| Swollen lymph nodes | 50% | Mild | Peak |
| Abdominal pain | 20% | Mild | Peak |
| Diarrhea | 8% | Mild | Peak |
| Vomiting | 15% | Mild | Peak |
| Fatigue | 80% | Mild | Any phase |
Transmission
Overview
Overview
Measles is a highly contagious viral disease caused by the measles virus (morbillivirus). It remains one of the most communicable infectious diseases, with a reproduction number (R₀) of approximately 12-18, meaning one infected person can spread the virus to up to 18 others in an unvaccinated population. Despite being vaccine-preventable, measles continues to pose risks to travelers visiting regions with lower vaccination coverage.
Transmission & Risk
Measles spreads through:
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Airborne droplets: When an infected person coughs or sneezes
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Direct contact: With respiratory secretions from infected individuals
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High transmissibility: The virus remains infectious in air for up to 2 hours after an infected person leaves a room
Travelers to regions with active measles outbreaks face significant risk, particularly those who are:
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Unvaccinated or partially vaccinated
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Traveling with unvaccinated children
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Born after 1957 without documented vaccination
Symptoms & Onset
Incubation Period: 7-21 days (average 10 days)
Classic Presentation (3-phase progression):
- Prodromal Phase (2-3 days): Fever (up to 40°C/104°F), cough, coryza (runny nose), conjunctivitis—often called the "3 Cs"
- Pathognomonic Signs: Koplik spots (white spots inside mouth) appear 2-3 days before rash
- Exanthema Phase (3-7 days): Characteristic maculopapular rash starting at hairline, spreading downward, lasting 4-7 days
Severity: Measles typically causes more severe illness than many other vaccine-preventable diseases, with complications occurring in 1 out of every 4 infected children.
Complications & Mortality
Serious complications occur in approximately 1-2 per 1,000 infected individuals:
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Pneumonia (most common complication, ~7% of cases)
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Encephalitis (brain inflammation, ~0.1% of cases)
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Subacute Sclerosing Panencephalitis (SSPE): Rare but fatal degenerative brain disease occurring 7-10 years after infection
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Secondary infections: Otitis media, sinusitis
Mortality: 0.2% in developed countries; up to 10% in low-resource settings with malnutrition
Prevention & Vaccination
Vaccine Effectiveness:
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1 dose: ~95% effective
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2 doses: >99% effective
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Immunity: Lifelong for vaccinated individuals
Recommended Vaccination:
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2 doses of MMR vaccine (measles, mumps, rubella)
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First dose: 12-15 months
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Second dose: 4-6 years or any time ≥28 days after first dose
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Adults born 1957 or later should have ≥2 documented doses or serological proof of immunity
Pre-Travel Considerations:
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Verify immunity 4-6 weeks before travel
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Request revaccination if immunity status is uncertain
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Immunocompromised individuals should consult healthcare providers before vaccination
Travel Advice
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High-risk destinations: Sub-Saharan Africa, parts of Asia, pockets of low vaccination coverage in developed countries
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Outbreak awareness: Check WHO travel advisories and local health departments for current measles activity
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Post-exposure guidance: If exposed to measles, vaccinated or unvaccinated individuals should seek medical evaluation immediately
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Isolation protocol: Infected travelers should remain isolated for 4 days after rash onset to prevent further transmission
Emergency Signs & When to Seek Help
Seek immediate medical attention if experiencing:
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High fever (>40°C/104°F) not responding to antipyretics
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Difficulty breathing or chest pain
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Severe headache or sensitivity to light
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Confusion or altered consciousness
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Signs of dehydration (no urination for >6 hours, severe thirst)
Diagnosis & Treatment
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Diagnosis: Clinical presentation + PCR testing, serology, or viral culture
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Treatment: Supportive care (no specific antiviral); vitamin A supplementation recommended
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Reportable disease: Measles is notifiable to health authorities in most countries
Key Statistics
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Causative Agent: Measles morbillivirus
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ICD-10 Code: B05
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ICD-11 Code: 1F03
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Incubation Period: 7-21 days
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Infectious Period: 4 days before rash to 4 days after rash onset
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Mortality Rate: 0.2-10% depending on healthcare access
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Vaccine-Preventable: Yes (highly effective)
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Notifiable Disease: Yes (mandatory reporting)
Overview
Measles is caused by Measles morbillivirus transmitted via airborne droplets. It remains a leading preventable cause of child mortality in low-vaccination regions despite a highly effective vaccine available since 1963.
Emergency Signs
Seek emergency medical care immediately if:
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Difficulty breathing, rapid breathing, or grunting
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Severe headache, neck stiffness, or altered consciousness (encephalitis)
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Seizures or convulsions
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Inability to drink or persistent vomiting
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Signs of severe dehydration (sunken eyes, no urination, extreme lethargy)
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Rash that becomes purple or looks like bruising (may indicate secondary infection)
Detailed Symptoms
Most common signs and symptoms
The disease progresses through two clinical phases:
Prodromal phase (2–4 days): High fever (up to 40°C/104°F), persistent cough, coryza (runny nose), and conjunctivitis — the classic "3 Cs". Koplik's spots (small bluish-white lesions on the inner cheeks) are pathognomonic and appear 1–2 days before the rash.
Exanthem phase (4–7 days): Characteristic maculopapular rash begins at the hairline and spreads cephalocaudally to the trunk and extremities over 3 days. Fever peaks at rash onset. Lymphadenopathy and splenomegaly may occur.
Knowing the symptoms is the first step to a quick response.
Course of Disease
Typical disease course:
- Incubation period: 10–14 days (range 7–21 days) from exposure to rash onset.
- Prodromal phase (2–4 days): High fever (often >40°C), cough, coryza (runny nose), conjunctivitis (the "3 Cs"). Koplik spots (pathognomonic blue-white spots on buccal mucosa) appear 1–2 days before rash.
- Exanthem phase (5–6 days): Maculopapular rash begins on the face/forehead, spreads cephalocaudally to trunk and extremities over 3 days. Fever typically peaks as rash appears, then declines.
- Recovery phase: Rash fades in order of appearance (face first), often with desquamation. Total illness duration: 7–10 days.
Infectivity: From 4 days before to 4 days after rash onset. Most contagious during prodromal phase. Basic reproduction number (R₀): 12–18 (one of the most transmissible human pathogens).
Diagnosis
How this disease is identified
Clinical diagnosis is supported by the characteristic rash pattern and Koplik's spots in an unvaccinated individual with fever and the 3 Cs. Laboratory confirmation:
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Serology: IgM antibody detection (positive 3 days after rash onset) — most practical
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RT-PCR: from nasopharyngeal swab, urine, or blood — most sensitive, confirms genotype
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Throat or urine culture: reference labs only Mandatory public health notification required in most countries.
Treatment
Available treatment methods
No specific antiviral therapy exists for measles. Management is supportive:
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Vitamin A supplementation: WHO recommends 200,000 IU on 2 consecutive days for children with measles — reduces mortality and complications by up to 50%
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Antipyretics (paracetamol/ibuprofen) for fever management
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Adequate hydration and nutrition support
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Secondary bacterial infection (otitis media, pneumonia): antibiotics as appropriate
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Hospitalization for complicated cases (encephalitis, pneumonia, severe dehydration)
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Ribavirin has been used in immunocompromised patients (off-label)
Most cases are effectively treated with early diagnosis.
Prevention Details
How to protect yourself
The MMR (Measles-Mumps-Rubella) vaccine provides >97% protection after two doses:
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Dose 1: 12–15 months of age
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Dose 2: 4–6 years of age (or at least 28 days after Dose 1)
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Post-exposure prophylaxis: MMR within 72 hours of exposure in susceptible individuals; immunoglobulin within 6 days for high-risk contacts (infants <12 months, immunocompromised, pregnant women)
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Herd immunity threshold: ~95% vaccine coverage required to prevent outbreaks WHO recommends 2-dose schedule for all children. Travelers to endemic regions should ensure vaccination is up to date.
Preparation is the best protection.
Travel Advice
Risk to travelers:
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High risk: Sub-Saharan Africa, parts of Asia, Pacific Islands during outbreaks. Moderate risk globally due to resurgence in Europe and North America.
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Ensure 2 doses of MMR vaccine before travel, regardless of destination.
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Infants traveling to high-risk areas may receive MMR from 6 months (does not count toward primary schedule — revaccinate at 12–15 months).
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In outbreak settings, avoid crowded indoor spaces; measles spreads in airborne particles that linger up to 2 hours after an infected person leaves.
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Report suspected measles immediately to local health authorities.
How common is it?
Statistics and geographic data
Globally, measles affects millions annually. WHO reported ~9 million cases and ~128,000 deaths in 2021, predominantly in children <5. Major outbreaks occurred 2018–2019 in Democratic Republic of Congo, Madagascar, Ukraine, Philippines, and USA. Africa and Southeast Asia carry the highest burden. Europe has experienced resurgence due to vaccine hesitancy. The R0 of 12–18 makes measles the most infectious respiratory pathogen known. Global coverage with 2-dose MCV2 reached 71% in 2021 (WHO target: 90%).
Risk Factors
Who is most at risk
Risk factors for acquiring measles:
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Lack of vaccination: The single most important risk factor. Unvaccinated individuals have a >90% chance of infection after exposure to the virus. Even one missed dose leaves a 7% susceptibility gap.
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International travel to endemic regions (sub-Saharan Africa, South/Southeast Asia, parts of Europe) without verified immunity.
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Crowded living conditions: Refugee camps, dormitories, military barracks, and densely populated urban areas facilitate rapid transmission.
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Healthcare settings: Nosocomial transmission is well-documented; the virus can linger in examination rooms for 2 hours after an infectious patient has left.
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Waning maternal antibodies: Infants aged 6–12 months lose maternally acquired protection and are not yet routinely vaccinated.
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Community under-vaccination: Localized pockets of low vaccination coverage (religious communities, areas with vaccine hesitancy) serve as outbreak epicenters.
Risk factors for severe disease and complications:
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Age extremes: Children under 5 years and adults over 20 years have the highest complication and mortality rates.
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Malnutrition: Particularly vitamin A deficiency, which increases the risk of corneal damage, severe pneumonia, and death by 2–3 fold.
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Immunocompromised status: HIV/AIDS, active chemotherapy, organ transplant recipients, and congenital immunodeficiencies. These patients may develop giant cell pneumonia (Hecht pneumonia) or measles inclusion body encephalitis (MIBE).
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Pregnancy: Measles during pregnancy increases risk of spontaneous abortion, premature delivery, and low birth weight.
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Overcrowding and poor access to healthcare: Delayed diagnosis and treatment significantly worsen outcomes.
Complications Details
Potential complications
Complications are more severe in infants, malnourished individuals, immunocompromised patients, and pregnant women:
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Otitis media: most common complication (1 in 10 cases)
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Pneumonia: leading cause of measles death (1 in 20 cases)
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may be viral or secondary bacterial
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Diarrhea and dehydration: especially dangerous in developing countries
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Encephalitis: 1 in 1,000 cases
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15% mortality, 25% long-term neurological sequelae
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Subacute sclerosing panencephalitis (SSPE): rare, fatal, progressive neurological disease appearing 7–10 years after infection (approximately 1 in 10,000 cases overall
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1 in 1,700–5,000 when infected before age 5)
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Blindness: due to vitamin A deficiency exacerbated by measles
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Immunosuppression: measles causes "immune amnesia," deleting immunological memory for months to years
Recovery & Outlook
Expected outcomes and recovery
Overall prognosis: Favorable in well-nourished individuals with access to supportive care. Case-fatality rate (CFR) is <0.1% in high-income countries but 3–6% in resource-limited settings, rising to 25% in malnourished children and displaced populations.
Complications affecting prognosis:
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Pneumonia (most common cause of measles death): 1–6% of cases.
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Encephalitis: ~1 in 1,000 cases; 15% fatality, 25% permanent neurological sequelae.
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Subacute sclerosing panencephalitis (SSPE): fatal degenerative CNS disease, onset 7–10 years after infection. Incidence: ~1 in 10,000 measles cases (higher if infected before age 2).
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Immune amnesia: measles destroys 11–73% of existing antibody repertoire, increasing susceptibility to other infections for 2–3 years post-recovery.
Recovery: Most uncomplicated cases resolve fully within 7–10 days. Lifelong immunity after natural infection.