Measles
What is Measles?
Measles is an extremely contagious and potentially severe viral disease that can easily cause outbreaks, especially in areas where people are not vaccinated or the population is under-vaccinated. Measles is so contagious that if one person has it up to 90% of non-immune people close to the infected person will be infected. Infected people can spread measles to others from 4 days before to 4 days after the rash appears.
Due to fewer people getting vaccinated, the United States is currently experiencing large outbreaks of measles. Get more information on our outbreaks page.
Below, you can explore how measles spreads, what the symptoms are, the serious complications of measles, how to prevent measles, and information about measles elimination in the U.S.
Measles is so contagious that if one person has it, up to 90% of non-immune people close to the infected person will be infected.
How does measles spread?
Measles is one of the most contagious diseases in the world. It spreads through the air when an infected person coughs or sneezes and can remain active on surfaces or in the air for up to two hours.
A person with measles can be contagious 4 days BEFORE the rash develops until 4 days AFTER the rash appears. Measles is so contagious that if one person has it, up to 9 out of 10 people around them will also become infected if they are not immune to measles or protected by vaccination.
What are the symptoms of measles?
Less signs and symptoms appear 7 to 14 days after exposure to the virus. Signs and symptoms of measles typically include:
- Koplik’s spots, tiny white spots inside the inner lining of the cheek
- High fever
- Cough
- Runny nose
- Sore throat
- Red eyes (conjunctivitis)
- A skin rash of red spots that starts at the head and spreads to the rest of the body. The rash may raise and join to form blotchy patches (not typically itchy).
- Ear infection
- Diarrhea
See the handout from CDC, AAP, and AAFP that lists the symptoms of measles by clicking the button below.
Measles virus can remain infectious on surfaces for up to 2 hours making it extremely difficult to contain and easy to transmit to others.
Measles Can Cause Serious Complications
Some people think of measles as just a rash and fever that clears up in a few days, but measles can cause serious health complications including:
Death
1–3 out of 1,000 people with measles will die, even with the best medical care available in the U.S.
Diarrhea and vomiting
Diarrhea and vomiting can cause the body to lose too much water, essential electrolytes, and nutrients (dehydration), leading to serious complications.
Ear infection
One of the most common complications of measles is a bacterial ear infection, affecting 1 in 10 children. Bacterial ear infections can lead to permanent hearing loss.
Croup, bronchitis, and laryngitis
The measles virus can cause swelling of the airways, often leading to a “barking” cough (croup), hoarseness, and difficulty breathing, particularly in young children. Inflammation of the inner airways can occur, leading to a productive cough (bronchitis). Inflammation of the voice box can lead to difficulty breathing and hoarseness (laryngitis).
Pneumonia
Measles can commonly cause an infection in the lungs (pneumonia). About 1 in 20 children who get measles will develop pneumonia. People with weakened immune systems can develop an especially dangerous type of pneumonia that can sometimes lead to death.
Encephalitis
About 1 in 1,000 people with measles develop a complication called encephalitis (inflammation of the brain). The condition can be especially dangerous for people with weakened immune systems. Encephalitis may occur right after measles infection, or months later. Encephalitis can cause seizures, cognitive impairment, and permanent brain damage.
Pregnancy problems
A measles infection during pregnancy is serious and can cause pneumonia in the mother and risks to the fetus, including miscarriage, stillbirth, low birth weight, and premature delivery. Measles vaccination is recommended BEFORE getting pregnant but is not given during pregnancy.
Immunity Amnesia
Researchers have shown that the measles virus wipes out 11–73 percent of the antibodies that protect against different viral infections and bacterial strains a person was previously immune to. Anything from influenza to herpesviruses to bacteria that cause pneumonia and skin infections can be forgotten by the body
A person with measles can be contagious 4 days BEFORE the rash develops until 4 days AFTER the rash appears.
How do you prevent measles?
The best way to protect yourself against measles is to be vaccinated with the MMR or MMRV vaccine. The measles virus, which is part of the MMR (measles, mumps, and rubella) vaccine, was first introduced in 1963. Before the vaccine was introduced, an estimated 48,000 people were hospitalized and 400–500 people died in the United States each year from measles.
Babies and Children
For the best protection against measles, your children need to receive the two recommended doses of the MMR (or MMRV, which also contains the vaccine for varicella [chickenpox]) vaccine. One dose of MMR vaccine is about 93% effective at preventing measles, and two doses are about 97% effective.
- First dose is given between 12–15 months of age
- Second dose is given between 4–6 years of age
In the event of an outbreak in the area, children can receive MMR as young as 6 months of age in addition to the regularly scheduled vaccines.
MMR vaccine is given later than some other childhood vaccines because antibodies transferred from mom to baby can provide some protection from disease and make the MMR vaccine less effective until around 1 year of age.
Adults
Adults who do not have evidence of immunity to measles should get at least one dose of MMR.
Some adults who got the measles vaccine between 1963–1967 received a killed virus version of the vaccine that is not as effective. It is recommended to be revaccinated with the current MMR if this is the case and you do not have immunity to measles.
It is assumed that most adults born before 1957 have immunity due to natural exposure to the virus and do not need to be vaccinated.
Please consult your doctor if you are concerned about your measles immunity status. There are tests to check for antibodies that can be performed to determine if you need an MMR vaccine.
It is imperative to be protected if there is a current outbreak in your area.
Measles was officially eliminated from the United States in 2000, meaning it is only found when someone contracts measles abroad and brings it back into the country. An outbreak can follow as this person spreads it among U.S. communities with pockets of unvaccinated people. This is why childhood vaccination is critical for preventing the spread of this highly contagious disease.
A massive measles outbreak centered in Texas in January of 2025, driven by an infected international traveler and fueled by a community of under- or nonvaccinated people, has led to pockets of outbreaks nationwide. The U.S. is expected to lose its elimination status in the spring of 2026.
Vaccines Stop Measles from Spreading
Measles is very contagious. Exposure to an infected person with measles will cause infections in 9 in 10 people who are not protected. Measles is serious and can be deadly, even in otherwise healthy children.
Immunization Schedules
To ensure that your family is up to date on their vaccines, view or download the childhood and adult immunization schedules and talk to your healthcare provider.
All people who are not vaccinated are susceptible to catching measles. It is rare to catch measles if you are vaccinated.
Children younger than 5 years old, adults over 20 years old, pregnant women, and people with weakened immune systems are at greatest risk of serious health complications from complications.
Adults at highest risk of contracting symptoms include:
- Students at post-high school education institutions
- Healthcare personnel
- International travelers
- People with weakened immune systems or who care for someone with a weakened immune system
- People with HIV
- People who are not vaccinated
Measles is not a seasonal virus. The virus spreads more rapidly during times of heavy travel or in situations where unvaccinated people are in close quarters with an ill person (like school or summer camp).
Measles kills about 100,000 people around the world each year, most of whom are children under the age of 5. There is no way to tell in advance how severe your child’s symptoms will be. See some fast facts below.
- About 1 in 5 unvaccinated people in the U.S. who get measles will be hospitalized.
- As many as 1 out of every 20 children with measles gets pneumonia, the most common cause of death from measles in young children.
- 1 out of every 1,000 people with measles will develop brain swelling (encephalitis), which could lead to brain damage.
- 1 to 3 out of 1,000 children with measles will die, even with the best care.
- Measles may cause pregnant women who have not had the MMR vaccine to give birth prematurely or have a low-birth-weight baby.
- In rare cases, the body’s immune response to the measles virus can cause brain swelling, which may result in a severe and potentially fatal condition called subacute sclerosing panencephalitis (SSPE). It typically develops years after a measles infection and is characterized by mental deterioration, muscle jerks, and seizures.
- An increase in the number of unvaccinated travelers bringing measles back to the U.S. from abroad
- Further spread of measles in U.S. communities with pockets of unvaccinated people
- Inaccurate and misleading information about vaccines leading people not to vaccinate against measles
There are currently measles outbreaks in the United States. Due to the rapidly changing outbreak situation, check the Measles Cases and Outbreaks web page, which is updated on a weekly basis. Please check regularly for information on outbreaks occurring in your area.
If you suspect you or one of your family members has been exposed to measles, call your doctor or local health department immediately. Please do not go directly to your doctor or healthcare provider. Measles is highly contagious, and you could infect others in the waiting room and/or while traveling to and from the doctor’s office. Your healthcare provider will be able to tell you the next steps to take to protect yourself, your family, and your community.
Not as long as you are immune to measles from previous infection or by vaccination. If you’re not sure whether you are fully vaccinated, talk to your doctor.
If you know that you got the “killed” (inactivated) version of the measles vaccine (an earlier formulation of measles vaccine that is no longer used) in 1963–1967, you should talk to your doctor about getting revaccinated with the current, live MMR vaccine. Not many people fall into this group; the “killed” version of the vaccine was given to less than 1 million people between 1963 and 1967.
If you’re unsure whether you fall into this group, you could ask your doctor to test your blood to determine whether you’re immune. Or you can get a dose of MMR vaccine. An extra dose of MMR vaccine is not harmful, even if you are already immune to measles.
If you’re unsure whether you’re immune to measles, you should first try to find your vaccination records or documentation of measles immunity. If you do not have written documentation of measles immunity, you should get vaccinated with the MMR vaccine. Another option is to have a doctor test your blood to determine whether you’re immune, but this option will take two doctor’s visits. There is no harm in getting another dose of MMR vaccine, even if you are already immune to measles.
Healthcare personnel should have documented evidence of immunity. Healthcare personnel without evidence of immunity should obtain two doses of MMR vaccine, separated by at least 28 days.
People 6 months of age and older who will be traveling internationally should be protected against measles. Before any international travel:
Infants 6–11 months of age should receive one dose of MMR vaccine. Infants who get one dose of MMR vaccine before their first birthday still need two more doses at the regularly recommended ages.
Children 12 months of age and older should receive two doses of MMR vaccine separated by at least 28 days.
Teenagers and adults who do not have evidence of immunity against measles with vaccine records or an antibody test, should get two doses of the MMR vaccine separated by at least 28 days.
