Measles is a serious infection that can cause severe complications, especially in young children, pregnant women, and people with weakened immune systems

Measles is caused by a virus that spreads through the air when an infected person coughs or sneezes. Most people who get measles will recover, but the infection itself is not mild — it causes high fever, rash, and body-wide symptoms that can last two weeks or longer. The real danger lies in what can happen during or after the infection: pneumonia, brain inflammation, and other complications that can be life-threatening.

Before the measles vaccine became widely used in the 1960s, measles killed hundreds of children every year in the United States alone. Today, deaths are rare in countries with high vaccination rates, but they still occur. Globally, measles remains a leading cause of preventable childhood death in areas with low vaccination coverage.

Key Takeaways

  • Measles can cause pneumonia, encephalitis (brain inflammation), and other serious complications that may require hospitalization.
  • Children under five, pregnant women, and people with weakened immune systems face the highest risk of severe illness and death.
  • One in every 1,000 children with measles develops encephalitis, which can cause permanent brain damage or death.
  • Even people who survive measles without obvious complications can develop a rare brain disease years later called subacute sclerosing panencephalitis (SSPE).
  • The measles vaccine prevents infection in about 97 percent of people who receive both doses, making prevention far safer than risking the disease itself.

Common complications that develop during measles infection

Pneumonia is the most common serious complication, occurring in about one out of every 20 infected children. The infection damages the lungs, making it hard to breathe, and pneumonia is the leading cause of measles-related hospitalization in children.

Encephalitis — inflammation of the brain — happens in about one out of every 1,000 people with measles. Symptoms include high fever, severe headache, confusion, seizures, and loss of consciousness. Some people recover fully, but others are left with permanent brain damage, deafness, or intellectual disability. A small number die.

Other complications that can occur include ear infections, diarrhea, croup (a breathing problem), and temporary vision problems. People with measles also become more vulnerable to bacterial infections because the virus weakens the immune system temporarily.

Who is at highest risk for severe measles

Children under five years old have the highest risk of serious complications and death. Their immune systems are still developing, and their bodies cannot fight the virus as effectively as older children and adults can.

Pregnant women who get measles face serious risks: the infection can cause miscarriage, premature birth, or birth defects. Babies born to mothers with measles may be born with the infection and develop severe disease in their first weeks of life.

People with weakened immune systems — including those with HIV, those undergoing cancer treatment, or those taking medications that suppress immunity — are at high risk for severe measles and complications. People with vitamin A deficiency also face worse outcomes, which is why doctors give vitamin A supplements to children with measles in areas where deficiency is common.

The rare but serious delayed complication: SSPE

Years or even a decade after recovering from measles, a small number of people develop subacute sclerosing panencephalitis (SSPE), a progressive brain disease caused by the measles virus. This happens in about one to two out of every 100,000 people who had measles, but the risk is higher in people who got measles before age two.

SSPE starts with behavior changes, memory problems, and mood changes. It progresses to seizures, loss of muscle control, and eventually coma and death. There is no cure. This disease is one of the reasons why preventing measles through vaccination is so important — once someone has measles, there is no way to prevent SSPE from developing later.

How doctors know measles is serious

A doctor will watch for warning signs during measles infection. High fever that does not come down, difficulty breathing, confusion, severe headache, or seizures are all signs that a complication is developing and the person needs hospital care.

Blood tests can confirm measles and rule out other infections. Chest X-rays may be done if pneumonia is suspected. If encephalitis is possible, a doctor may do a spinal tap (lumbar puncture) to check the fluid around the brain and spinal cord.

Most people with measles are treated at home with rest, fluids, and fever-reducing medicine. People with complications need hospital care, where doctors can provide oxygen if breathing is difficult, manage seizures, and treat secondary infections.

Why measles spreads so easily

Measles is one of the most contagious diseases known. One person with measles will infect 12 to 18 other people in an unvaccinated population. The virus spreads through tiny droplets in the air that can travel across a room and linger for up to two hours after an infected person leaves.

This means measles can spread before a person even knows they have it — the rash does not appear until three to seven days after infection begins. During those early days, when symptoms feel like a cold or flu, the person is highly contagious and may infect others without realizing it.

Measles severity in vaccinated versus unvaccinated people

Unvaccinated people who get measles face the full force of the infection and all its possible complications. Vaccinated people who somehow get infected (which is rare) typically have milder symptoms and much lower rates of complications.

The measles vaccine is about 97 percent effective at preventing infection when both doses are given. The first dose is usually given at 12 to 15 months of age, and the second dose at four to six years old. People who received both doses have strong, lasting protection.

Even in the rare cases where a vaccinated person gets measles, the infection is usually less severe because their immune system recognizes the virus and fights it more effectively from the start.

What happens after measles infection

Most people who survive measles develop lifelong immunity — they cannot get measles again. However, they may carry the memory of the infection for years: some people report that measles left them feeling weak or fatigued for weeks afterward.

The real concern after measles is SSPE, the delayed brain disease described above. There is no way to know who will develop it, which is why prevention through vaccination remains the safest choice.

Frequently Asked Questions

Can measles kill an adult?

Yes, though death is less common in healthy adults than in young children. Adults over 20 who get measles have higher rates of pneumonia and other complications than teenagers. Pregnant women and adults with weakened immune systems face particularly high risk of severe disease and death.

Is measles worse than the flu?

Measles is generally more serious than seasonal flu. Measles causes higher fever, lasts longer, and has higher rates of serious complications like pneumonia and encephalitis. The flu can also be severe, but measles is considered more dangerous overall, especially in young children.

What should I do if I think I have measles?

Call your doctor or hospital before going in — tell them you think you have measles so they can prepare and prevent spreading it to others in the waiting room. Do not go to a public place. Stay home, rest, drink fluids, and follow your doctor's instructions. Seek immediate care if you have difficulty breathing, severe headache, confusion, or seizures.

Can you get measles twice?

No. Once you recover from measles, your immune system remembers the virus and protects you for life. Getting the measles vaccine provides the same lifelong protection without the risk of the disease itself.

Why is the measles vaccine important if measles is rare now?

Measles is rare in countries with high vaccination rates because so many people are protected. If vaccination rates drop, measles comes back quickly — outbreaks have occurred in communities where vaccination rates fell below 90 percent. The vaccine keeps measles rare by preventing it from spreading in the first place.