Measles: What to Know
Learn key facts about symptoms, how it spreads, who is at risk, and how it can be prevented.
Reviewed by Georges Benjamin, MD, and Carlos del Rio, MD. Last updated April 3, 2025.
Measles is an extremely contagious virus that can lead to severe complications, including death and permanent disability. It is a vaccine-preventable disease that has been largely eliminated in the United States. However, currently, several US states are experiencing unusually large outbreaks, including Texas and New Mexico. The outbreaks are primarily affecting children and adults who have not been vaccinated (with the MMR or MMRV vaccine).
What are the symptoms of measles?
Symptoms appear 7-14 days after a person is exposed to the virus. They include a high fever that comes and goes (sometimes 104°F or higher), a dry cough, fatigue, sore throat, body aches, a runny nose, and red and watery eyes. These symptoms usually last for about a week.
A few days after these symptoms begin, a red rash appears on the face before spreading to the whole body. The rash does not itch. The infection also causes tiny spots inside the mouth on the inner lining of the cheek called “Koplik’s spots.”
What complications can be caused by measles?
Measles can cause serious and life-threatening complications. The most common complications include ear infections (1 in 10 cases), diarrhea (less than 1 in 10 cases), and pneumonia (1 in 20 cases). Pneumonia the leading cause of measles-related death in young children. Other serious but rare complications include:
- Brain swelling (encephalitis), which can cause seizures, brain damage, or death (1 in 1,000 cases).
- A brain disease called subacute sclerosing panencephalitis, which causes progressive neurological decline, coma, and death. This disease occurs 2-10 years after measles infection.
- Eye damage, including blindness.
- Miscarriage or the death of a pregnant woman.
How is measles diagnosed and treated?
If you suspect you have been infected, see a health care provider right away. Diagnosis involves evaluation of symptoms as well as laboratory testing of blood, nasal swabs, or urine.
Symptoms can be treated by rest, hydration, and medications to treat fever, pain, and cough. If bacterial infections develop, such as ear infections or pneumonia, antibiotics may be needed. Patients who are hospitalized with breathing difficulties may receive oxygen support.
For people who are malnourished, vitamin A supplements can be helpful to limit eye damage. Large amounts of vitamin A can have toxic effects on the liver, so it must be given under a doctor’s supervision. Vitamin A does not prevent measles and is not a substitute for vaccination.
Who is most at risk from measles?
People who have not been vaccinated are most at risk. Infants under 12 months old are at high risk because the first dose of the MMR or MMRV vaccine is not given until 12-15 months of age. However, newborns may be protected for up to 6 months if the mother was vaccinated before pregnancy.
A vaccine is available for infants between 6 and 11 months old who are living in an area with an active outbreak or will be traveling internationally. Babies who receive this vaccine will still need two doses of the MMR or MMRV vaccine at 12-15 months and 4-6 years.
Other high-risk groups include people with weakened immune systems (for example, people with cancer or organ transplants), and people with nutritional deficiencies.
How does measles spread?
Measles is one of the most contagious viruses in the world. It is far more contagious than COVID-19 or the flu. The virus spreads through respiratory droplets produced when people cough, sneeze, or talk. Particles of the virus can remain suspended in the air for at least two hours. It can also be spread by touching contaminated surfaces, such as toys and doorknobs. People infected with the virus can spread it to others up to four days before and four days after the rash develops.
What is the incidence of measles in the United States?
Before a vaccine was introduced in 1963, nearly every child in the United States got measles by the age of 15. Every year, there were 3-4 million cases, 48,000 hospitalizations, and 400-500 deaths. After vaccination became common, the number of cases dropped by 99 percent. In the past 5 years, the number of cases has ranged from just 13 in 2020 to 285 in 2024.
In the first 3 months of 2025 alone, there were already over 400 cases reported, putting the nation on track for the largest outbreak in recent history. You can track the current numbers on the Centers for Disease Control and Prevention’s website.
How can measles be prevented?
Measles can only be prevented by getting vaccinated. Doctors recommend that children receive two doses of the MMR vaccine (measles, mumps, and rubella) or the MMRV vaccine (measles, mumps, rubella, and varicella). The first dose is between 12 and 15 months old, and the second dose is between 4 and 6 years old. These vaccines offer lifelong protection.
In areas with an active outbreak, you can help reduce the spread through adequate vaccination, handwashing and mask-wearing.
Is the MMR vaccine effective?
The MMR vaccine is highly effective. Receiving two doses reduces a person’s likelihood of infection by 97%. If at least 95% of the US population is fully vaccinated against measles, large outbreaks can be entirely prevented.
Is the MMR vaccine safe?
The MMR vaccine is safe for most people. A 2012 National Academies report found that, in rare cases, such as for people who are immunocompromised, the vaccine can cause serious complications. These include febrile seizures, anaphylaxis, and a condition called measles inclusion body encephalitis. The vaccine can also cause temporary joint pain for women and children. The MMR vaccine does not cause autism or type 1 diabetes.
The report contains a full analysis of possible complications from the MMR vaccine, including links to scientific studies.
Why do measles outbreaks still occur?
The virus is often spread by travelers who return to the United States from countries with outbreaks. To prevent these isolated cases from becoming outbreaks in the United States, at least 95% of the population needs to be vaccinated (a concept known as “herd immunity” or “community immunity”). In the 2023-2024 school year, only 92.7% of kindergartners were vaccinated nationwide. Some states reported higher vaccine coverage – such as West Virginia at 98.3% – while some reported much lower coverage, such as Idaho at 79.6%.
Low vaccination rates can be driven by concerns about vaccine safety (known as “vaccine hesitancy”) or religious or philosophical objections to vaccination. In addition, many children missed appointments for routine vaccinations during the COVID-19 pandemic, which has resulted in lower levels of community vaccination levels.
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Disclaimer: The information provided on this website is for informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition.
