Measles can cause serious complications, especially in young children, adults over 20, and people with weakened immune systems
Measles itself starts as a respiratory infection—fever, cough, runny nose—that most people recognize as flu-like. But measles is far more contagious than flu, and the virus damages the immune system in ways that can lead to dangerous secondary infections. The real danger is not always the measles rash itself, but what happens while your body is fighting the virus.
Complications occur in roughly one out of every four to five people who get measles, though the rate is higher in certain groups. Pneumonia is the most common serious complication in children under five. Encephalitis (brain inflammation) is rare but can cause permanent brain damage or death. Other complications include ear infections that cause hearing loss, miscarriage in pregnant women, and a condition called subacute sclerosing panencephalitis (SSPE), which develops years later and is always fatal.
Key Takeaways
- Measles kills roughly one to two people per thousand infected in developed countries, and far more in places with malnutrition or limited medical care.
- Children under five, adults over twenty, pregnant women, and people with HIV or cancer have the highest risk of serious complications.
- Pneumonia develops in one out of every twenty infected children and is the leading cause of measles death in children.
- Encephalitis occurs in one to two per thousand cases and can cause permanent disability even if the person survives.
- SSPE is a fatal brain disease that can develop six to ten years after measles infection, even in people who recovered normally.
Who is at highest risk of severe measles
Age matters more than almost anything else. Children under five have the highest complication rate, particularly those under two. Adults over twenty also face higher risk than teenagers and young adults. Pregnancy is a major risk factor—measles increases the chance of miscarriage and premature birth, and infected newborns face severe disease.
People with weakened immune systems are at extreme risk. This includes anyone with HIV (especially with a low CD4 count), anyone undergoing chemotherapy for cancer, and people taking immunosuppressive drugs after organ transplant. Vitamin A deficiency also increases severity, which is why measles is more dangerous in countries with widespread malnutrition.
Pneumonia and respiratory complications
Pneumonia is the most common serious complication of measles in children, occurring in roughly five percent of infected children under five. The virus damages the lining of the lungs, making it easy for bacteria to move in and cause secondary infection. A child with measles pneumonia will have worsening cough, shortness of breath, and chest pain even as the rash appears.
Croup (a barking cough caused by throat swelling) also occurs during measles and can block the airway in young children. Both conditions require hospital care. In developing countries where antibiotics or oxygen may not be available, pneumonia is the leading cause of measles death.
Brain inflammation and neurological damage
Encephalitis (swelling of the brain) occurs in one to two per thousand measles cases and is more common in adults than children. Symptoms include high fever, severe headache, confusion, seizures, and sometimes coma. Some people recover fully; others are left with permanent brain damage, deafness, intellectual disability, or paralysis.
A separate condition called SSPE develops years after measles infection—typically six to ten years later, but sometimes decades. It causes progressive brain damage: personality changes, memory loss, jerking movements, and eventually death. SSPE is always fatal, usually within one to three years of symptom onset. It occurs in roughly one to two per hundred thousand measles cases, but the risk is higher if measles infection happened before age two.
Measles in pregnancy and newborns
Pregnant women with measles face higher risk of severe pneumonia and other complications. Measles infection during pregnancy increases the risk of miscarriage, stillbirth, and premature delivery. Infants born to infected mothers may have low birth weight and are at risk for congenital measles—a severe form of the disease that can cause blindness, deafness, heart defects, and intellectual disability.
Newborns infected with measles in the first few months of life have higher death rates than older children. They are also at higher risk for SSPE later in childhood.
Death rates and long-term outcomes
In developed countries with access to hospital care, measles kills roughly one to two people per thousand infected. In countries with malnutrition, limited antibiotics, or no intensive care, death rates can reach five to ten percent or higher. Children under five account for most measles deaths worldwide.
Even survivors of serious measles complications may face lasting effects. Encephalitis survivors sometimes have permanent hearing loss, seizure disorders, or cognitive problems. Pneumonia can lead to chronic lung damage. The psychological impact of SSPE—knowing the disease will be fatal—affects entire families.
Why measles is more dangerous than it appears
Measles spreads so easily (one infected person infects twelve to eighteen others in an unvaccinated population) that large outbreaks create a surge of cases all at once. Hospitals fill with measles patients, and people with other emergencies—heart attacks, severe injuries, appendicitis—cannot get beds or staff attention. This "crowding effect" increases death rates even in developed countries during large outbreaks.
The virus also temporarily suppresses the immune system, making people vulnerable to other infections for weeks after measles resolves. Ear infections, sinus infections, and bacterial pneumonia are common in this window. Some of these secondary infections cause permanent damage—measles is a leading cause of hearing loss in children in countries without vaccination programs.
Frequently Asked Questions
Can measles kill you if you are vaccinated?
Measles vaccine is roughly ninety-seven percent effective at preventing infection after two doses. The small number of vaccinated people who do get measles typically have milder disease with lower complication rates. Death in a vaccinated person is extremely rare.
Is measles dangerous if you had it as a child and recovered?
Recovery from measles gives lifelong immunity—you cannot get measles again. However, SSPE can develop years later even in people who had normal recovery. SSPE risk is higher if infection occurred before age two, but it can happen at any age.
What should I do if I think I have measles?
Contact your doctor or hospital before going in person, so they can prepare for a highly contagious patient. Do not go to a waiting room where you might infect others. Treatment focuses on managing fever and symptoms while your immune system fights the virus; there is no medicine that kills measles directly. Hospital care is needed if you develop difficulty breathing, confusion, or severe fever.
Can measles cause problems years after infection?
Yes. SSPE is a fatal brain disease that develops six to ten years after measles (sometimes longer), causing progressive neurological damage. It is rare but always fatal. Some people also develop chronic conditions like seizure disorders after encephalitis.
Why is measles more dangerous in poor countries?
Malnutrition weakens the immune system and increases complication rates. Limited access to antibiotics means bacterial pneumonia cannot be treated. Lack of oxygen, blood transfusions, and intensive care means more people die from preventable complications. Measles death rates are ten to fifty times higher in countries without these resources.