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Disease

Measles

Learn about measles, including its symptoms, diagnosis, laboratory tests, treatment and prevention.

Last Reviewed 26 Jul 2026
Reading Time 8 min read

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.

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Key Fact

The measles virus can remain infectious in the air of a room for up to two hours after an infected person has left it. Someone is also contagious for about four days before the rash even appears, which is part of why the virus spreads so easily.

Warning

Difficulty breathing, a high fever that will not come down, or unusual drowsiness or confusion are medical emergencies. Seek immediate care rather than waiting to see if symptoms improve.

AT A GLANCE

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.
Important
Because measles is so contagious, a suspected case is often treated as measles, with isolation precautions started, while confirmatory test results are still pending.

Laboratory Tests

Measles IgM Antibody Test

Detects the immune system’s early response and confirms a current or recent measles infection.

Sample Venous blood
Time 24–72 hours

Measles IgG Antibody Test

Helps confirm past infection or immunity, sometimes used alongside the IgM test.

Sample Venous blood
Time 24–72 hours

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.

Sample Throat swab, nasal swab, or urine
Time 24–48 hours

Complete Blood Count (CBC)

Does not confirm measles on its own but can help assess overall health and rule out other causes of fever.

Sample Venous blood
Time 30–60 minutes

Laboratory Note

Laboratory confirmation matters most for outbreak tracking and for cases where the diagnosis is not clinically obvious. Treatment decisions are usually made on clinical grounds without waiting for results.

Treatment

Supportive Care

Rest, fluids, and fever management support recovery, since there is no specific antiviral medicine for measles.

Route Oral or Intravenous (IV)
Duration Throughout the illness, typically 2–3 weeks

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.

Route Oral
Duration Two doses, given 24 hours apart

Treatment Note

Antibiotics have no effect on the measles virus itself but may be prescribed to treat bacterial complications such as ear infections or pneumonia.

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.

Prevention Note

Vitamin A supplementation does not prevent measles and is not a substitute for the MMR vaccine. Vaccination remains the only reliable way to prevent infection.

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

Risk Note

Because measles spreads so easily, even brief contact with an infected person in a shared space can be enough to catch it if you are not immune.

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.

Complication Note

Most children recover from measles without lasting effects, especially with prompt supportive care and vitamin A supplementation where appropriate. Complications are more likely in children under five, adults over twenty, and people with weakened immune systems.

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.

Emergency Advice

Measles can be serious at any age but is especially risky for young children, pregnant women, and anyone with a weakened immune system. Do not wait to seek care if danger signs develop.

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.

Prognosis Note

Measles remains one of the leading vaccine-preventable causes of death among young children worldwide, particularly where vaccination coverage is low. Vaccination has prevented millions of deaths globally.

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.

Clinical Note

The distinctive pattern of fever followed by Koplik spots and then a descending rash helps distinguish measles from other rash-causing illnesses, though laboratory confirmation is useful during outbreaks or uncertain cases.

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.