Measles is a highly contagious viral infection that causes fever, cough, rash, and other symptoms. Measles can lead to serious health problems, especially in young children, pregnant women, and people with weakened immune systems. Most people recover fully, but some develop complications that can be permanent or fatal. Although measles is preventable with vaccination, outbreaks still occur in areas with low vaccine coverage.

Measles is a viral illness caused by the measles virus. The condition is sometimes called rubeola. Measles usually starts with cold-like symptoms, followed by a rash that begins on the face and moves down the body.

Measles is one of the most contagious diseases known, and it can spread quickly in communities where people are not protected by vaccination or past infection. Today, measles is uncommon in countries with high vaccination rates but remains common in some regions.

Measles spreads very easily from person to person mainly through aerosols in the air and less often by contact with contaminated surfaces. The virus multiplies in the nose and throat of someone with measles and spreads into the air when that person breathes, coughs, sneezes, or talks. Infectious aerosols that contain the virus can stay in the air for two hours after a person with measles has left the room. Measles is so contagious that about 90% of people who are not immune will get infected if they are exposed to the virus.

A person with measles can spread the virus from five days before the rash appears through the fourth day after it appears. People may not realize they are contagious, which makes it easy for the virus to spread in homes, schools, airports, and other public places. Outbreaks often happen in crowded settings or where vaccination rates are low.

Risk factors for measles include being unvaccinated, traveling to areas where measles is common, and having a weakened immune system. The main risk factors are:

• Not receiving the measles vaccine or receiving only one of the two recommended doses
• Being too young to receive the first dose of the measles vaccine, usually given at 12 to 15 months
• Having a medical condition that prevents vaccination, such as a weakened immune system caused by illness, medicines, or poor nutrition
• Living in or traveling to an area that has frequent measles cases or a current outbreak
• Having contact with someone who has measles, especially in crowded places such as schools, childcare, or doctors’ offices

Infants and pregnant women who become infected are at higher risk of serious illness.

Symptoms of measles often follow a typical pattern and usually start 10 to 14 days after getting exposed to the virus. The main symptoms are:

• Fever, which can become high
• Cough, which may not go away quickly
• Runny nose, sometimes with sneezing
• Red, watery, or inflamed eyes (conjunctivitis), sometimes with sensitivity to light
• Sore throat
• A general feeling of being unwell
• Tiny white or bluish spots inside the mouth, called Koplik spots (these spots appear before the rash)
• A red, blotchy rash that usually starts on the face and behind the ears, then spreads down the body to the trunk, arms, and legs (the rash may last four to seven days and can join together in large patches)
• Muscle aches
• Swollen lymph nodes

People should contact a doctor promptly if they or someone they care for has a high fever, trouble breathing, confusion, ongoing vomiting, seizures, or signs of dehydration during or after a suspected measles infection.

If people have been exposed to measles and are seeking healthcare, it is very important that they call ahead to let the provider know they are worried they have been exposed or may have measles, so that the provider can take appropriate precautions to protect other patients and staff.

Diagnosis of measles is based on symptoms, physical exam findings, and laboratory tests. Doctors suspect measles when a person has a fever, rash, and other typical symptoms. They are more likely to suspect it if the person is known to have been exposed to the virus or has traveled to an area with measles.

The doctor will ask about symptoms and recent exposure to measles, and will look for signs such as cough, runny nose, red eyes, and the typical measles rash. Koplik spots inside the mouth can help confirm measles but are not always present.

Laboratory tests used to confirm measles include:

• A reverse transcription polymerase chain reaction (RT-PCR) test, which finds genetic material from the measles virus in a sample from the throat, is the preferred test
• A paired immunoglobulin G (IgG) antibody test, a blood test that compares antibody levels during the illness and again after recovery, to see whether they rose in response to the infection, can be done but does not replace the RT-PCR

Doctors may also order additional tests to rule out other illnesses with similar signs and symptoms.

Treatment for measles focuses on relieving symptoms and preventing complications, because there is no specific antiviral medicine for the measles virus.

Main treatments include:

• Rest and fluids to prevent dehydration
• Medicines that reduce fever and discomfort, such as acetaminophen or ibuprofen
• Breathing humidified air, which may help relieve symptoms
• Vitamin A supplements, which are given to children with measles, especially in areas where vitamin A deficiency is common, to lower the risk of severe illness and complications
• Antibiotics do not work against measles and are used only if a secondary bacterial infection, such as pneumonia or an ear infection, develops during measles
• Supportive hospital care, such as intravenous fluids or supplemental oxygen, which may be needed for people with severe symptoms, breathing problems, or complications

Public health officials will help ensure that people with measles isolate at home, away from others, through the fourth day after the rash appears, to prevent spreading the virus.

Complications of measles can affect many parts of the body and are more likely in young children, people with weakened immune systems or poor nutrition, and pregnant women. Complications may include:

• Pneumonia, a lung infection that is the leading cause of death from measles, especially in children
• Diarrhea, which can lead to dehydration and worsen nutrition
• Ear infections, which may cause pain and, in some cases, hearing loss
• Encephalitis (inflammation of the brain), which can cause seizures, confusion, or long-term brain damage, and occurs in about 1 in 1,000 cases
• Bronchitis or croup, which involves swelling of the airways
• Blindness, which can result from eye infections or a lack of vitamin A
• A low count of platelets (the cells that help blood clot), which can cause bleeding and bruising
• Subacute sclerosing panencephalitis, a rare and fatal brain disorder that develops years after measles, most often in people who were infected at a young age
• Pregnancy complications, including miscarriage, premature birth, or low birth weight

Severe symptoms that develop during or after measles need prompt medical attention.

Measles can be prevented through vaccination and other measures. The measles-mumps-rubella (MMR) vaccine is highly effective and safe, providing long-lasting protection after two doses.

Prevention strategies include:

• Routine MMR vaccination for children, usually given in two doses, with the first at 12 to 15 months and the second at 4 to 6 years
• Catch-up vaccination for older children, teens, and adults who missed earlier doses or do not know their vaccination history
• Vaccination during outbreaks or before travel to areas with frequent measles cases
• Immune globulin, a blood product that contains antibodies, given within six days of exposure to people who cannot receive the vaccine, such as infants, pregnant women, or those with certain immune problems

Vitamin A does not prevent measles but is used to reduce complications in those who become infected.

The outlook for most people with measles is generally good, especially in healthy children and adults who receive proper care. Most people recover fully within a few weeks without lasting problems but can be more susceptible to other infections afterward. However, measles can cause complications, and the risk of serious illness and death is higher in young children, people with weakened immune systems or poor nutrition, and pregnant women.

In countries with strong healthcare systems and high vaccination rates, deaths from measles are rare. Where access to care is limited or vaccine coverage is low, measles can lead to severe illness, long-term disability, or death.

Prevention through vaccination remains the best way to improve the outlook for individuals and communities.

This article was medically reviewed in November 2026.