Overview
A high fever, a cough, red and watery eyes, and then a rash that starts on the face and works its way down the body over the following days. That is the shape measles usually takes, and it is one of the most contagious illnesses there is, far more so than most people realise.
Disease Summary
- Category
- Infectious Disease
- Cause
- Measles virus (Measles morbillivirus), a highly contagious paramyxovirus
- Transmission
- Airborne and respiratory droplets; can remain infectious in the air or on surfaces for up to two hours
- Body System
- Respiratory System
- Preventable
- Yes
- Curable
- Yes
Symptoms
Common Symptoms
Measles usually develops in a fairly predictable order, starting several days before the rash appears.
Fever
Often high, and usually the first sign to appear, some days before the rash.
Cough and Runny Nose
A persistent cough alongside a runny nose typically develops early in the illness.
Red, Watery Eyes
Conjunctivitis, eyes that are red, watery, and sensitive to light, commonly accompanies the fever and cough.
Tiny White Spots in the Mouth
Known as Koplik spots, these small white spots inside the cheeks often appear two to three days before the rash and are a distinctive early clue.
Rash
A red, blotchy rash usually begins on the face and hairline, then spreads down to the trunk, arms, and legs over the following days.
Danger Signs
Seek emergency medical attention immediately if any of the following develop.
Difficulty Breathing
Rapid or laboured breathing can signal pneumonia, the most common cause of death from measles in young children.
Unusual Drowsiness, Confusion, or Seizures
These can indicate encephalitis, swelling of the brain, and require emergency care.
Signs of Dehydration
Little or no urination, sunken eyes, or extreme thirst can develop quickly, especially alongside diarrhoea.
High Fever That Will Not Come Down
A fever that persists despite treatment needs prompt medical review.
Diagnosis
Clinical Assessment
Doctors often recognise measles from the combination of fever, cough, red eyes, and the characteristic rash, particularly during a known outbreak.
Blood Test for Measles Antibodies (IgM)
Confirms a recent measles infection and is the most common way to verify the diagnosis.
PCR Testing
Detects the virus directly from a throat swab, nasal swab, or urine sample, and can confirm the diagnosis even before antibody levels rise.
Laboratory Tests
Measles IgM Antibody Test
Detects the immune system’s early response and confirms a current or recent measles infection.
Measles IgG Antibody Test
Helps confirm past infection or immunity, sometimes used alongside the IgM test.
RT-PCR Testing
Detects the virus’s genetic material directly, useful early in the illness or to confirm the specific measles strain during an outbreak.
Complete Blood Count (CBC)
Does not confirm measles on its own but can help assess overall health and rule out other causes of fever.
Treatment
Supportive Care
Rest, fluids, and fever management support recovery, since there is no specific antiviral medicine for measles.
Vitamin A Supplementation
Recommended by the WHO for children diagnosed with measles, particularly in areas where vitamin A deficiency is common. It can reduce the risk of severe complications and death, though it does not prevent measles and is not a substitute for vaccination.
Prevention
Get the MMR vaccine
Two doses of the measles, mumps, and rubella (MMR) vaccine offer strong, long-lasting protection and are the most effective way to prevent measles.
Check vaccination status before travel
Travellers to areas with ongoing measles activity should confirm they are fully vaccinated at least two weeks before departure.
Avoid contact with infected individuals
Since measles spreads easily through the air, avoiding close contact with someone who has a suspected or confirmed case reduces the risk of transmission.
Support community vaccination coverage
High vaccination rates within a community protect those who cannot be vaccinated themselves, such as very young infants or people with weakened immune systems.
Risk Factors
Higher Risk of Severe Illness
These groups face a greater chance of severe illness or complications if infected.
- Children under 5
- Adults over 20
- Pregnant women
- People with weakened immune systems
Increased Chance of Infection
These groups have a higher chance of being exposed to the measles virus.
- Unvaccinated individuals of any age
- People living in or travelling to areas with active measles outbreaks
Exposure Factors
Conditions that increase the risk of exposure or worsen outcomes.
- Vitamin A deficiency, more common where access to a varied diet is limited
- Crowded living or gathering conditions
Complications
Pneumonia
The most common cause of death from measles in young children.
Encephalitis
Swelling of the brain that can cause seizures and lead to lasting disability, though it is uncommon.
Severe Diarrhoea and Dehydration
Can develop quickly, particularly in young children, and requires prompt fluid replacement.
When to Seek Medical Care
Difficulty Breathing
Rapid or laboured breathing needs urgent medical attention.
Unusual Drowsiness, Confusion, or Seizures
A change in alertness or new seizures require emergency care.
Signs of Dehydration
Little or no urination, sunken eyes, or extreme thirst should be assessed promptly.
Fever That Persists Beyond a Few Days
A fever that does not improve, or that returns after initially settling, should be reviewed by a healthcare provider.
Prognosis
Good for Most People
Most people recover within two to three weeks with supportive care.
Complications Are More Likely in Certain Groups
Young children, adults over twenty, pregnant women, and people with weakened immune systems face a higher risk of severe illness.
A Rare Late Complication Can Occur Years Later
Subacute sclerosing panencephalitis (SSPE) is a very rare but fatal condition that can develop several years after a measles infection, most often in those infected before the age of two.
Differential Diagnosis
Rubella
Rubella causes a similar rash but is generally much milder, with a shorter illness and fewer complications.
Malaria
In the days before the rash appears, measles can resemble malaria or other fever-causing illnesses common in the region, and should be considered and ruled out.
Roseola
Common in young children, roseola causes a high fever followed by a rash, but the rash typically appears as the fever breaks rather than days into the illness.
References
World Health Organization (WHO)
World Health Organization fact sheet on measles transmission, symptoms, diagnosis, treatment, and prevention.
Centers for Disease Control and Prevention (CDC)
Clinical and public health guidance on measles causes, symptoms, and complications.
CDC Clinical Overview of Measles
Clinical guidance for healthcare providers on measles diagnosis, laboratory testing, and the role of vitamin A in management.
Frequently Asked Questions
Is measles contagious?
Yes, extremely. Measles is one of the most contagious illnesses known, spreading through the air and remaining infectious in a room for up to two hours after an infected person has left.
Does vitamin A prevent measles?
No. Vitamin A can reduce the severity of measles once someone is infected, particularly in areas where vitamin A deficiency is common, but it does not prevent infection. The MMR vaccine is the only reliable way to prevent measles.
Can adults get measles?
Yes. Anyone who is not vaccinated and has not previously had measles can be infected, and adults over twenty face a higher risk of complications than older children.
How long does measles last?
The rash typically lasts five to six days, and most people recover within two to three weeks overall.