Measles is a viral infection that spreads through the air and causes fever, rash, and cough

Measles is caused by a virus that travels in droplets when an infected person coughs or sneezes. You catch it by breathing in those droplets or by touching a surface where they landed and then touching your face. The infection starts in the lungs and spreads through the body, triggering a characteristic rash that appears several days after fever begins. Most people recover, but measles can cause serious complications, especially in young children, pregnant women, and people with weakened immune systems.

The virus is highly contagious — if one person has measles and is not immune, about 9 out of 10 people around them will catch it. This is why measles spreads quickly in communities where vaccination rates are low. Once you have had measles or been vaccinated against it, you are protected for life.

Key Takeaways

  • Measles spreads through the air when an infected person coughs or sneezes, making it one of the most contagious viral infections.
  • Symptoms appear in stages: fever and cough first, followed by a rash that starts on the face and spreads downward.
  • Serious complications include pneumonia, brain inflammation, and ear infections, which occur more often in children under five and adults over twenty.
  • The MMR vaccine prevents measles and is given in two doses starting at age one, with protection lasting a lifetime.
  • There is no specific treatment for measles itself — care focuses on managing fever and preventing dehydration while the immune system fights the virus.

How measles starts and what the first symptoms look like

Measles begins with what looks like a cold or flu. You develop a fever, usually between 101°F and 104°F, along with a cough, runny nose, and sore throat. Many people also have red, watery eyes and feel tired. These symptoms last two to three days, then may seem to improve slightly before the rash appears.

Before the rash shows up, you may notice small white spots inside your mouth on the cheeks opposite your molars. These spots, called Koplik spots, look like grains of salt on a red background and are a sign measles is present. They appear two to three days before the rash and fade as the rash develops. If you see these spots and have fever and cough, measles is likely the cause.

The rash and how it progresses

The measles rash appears three to seven days after fever starts and looks like small, flat red spots that may have a slightly raised center. It begins on the face and hairline, then spreads down the neck, trunk, and limbs over the next few days. The rash is itchy but does not blister or leave scars. As it spreads, the spots may blend together, giving the skin a flushed appearance.

The rash peaks around day five or six of illness and then begins to fade, usually disappearing within a week. The order matters: rash on the face first, then spreading downward. This pattern helps doctors tell measles apart from other rashes. Fever usually drops as the rash appears, though some people remain feverish for several days.

Serious complications that can develop

Most people recover from measles without lasting problems, but complications occur in about one out of every ten cases. The most common is pneumonia, which develops when the measles virus or a secondary bacterial infection affects the lungs. Pneumonia causes difficulty breathing, chest pain, and can require hospitalization.

Encephalitis — inflammation of the brain — is rare but serious and can cause seizures, confusion, and permanent brain damage. Subacute sclerosing panencephalitis (SSPE) is an extremely rare but fatal condition that develops years after measles infection, usually in people who were infected before age two. Ear infections, diarrhea, and febrile seizures also occur, particularly in young children. Pregnant women who get measles face higher risk of miscarriage and premature birth. People with weakened immune systems from HIV, cancer treatment, or organ transplant are at highest risk for severe disease.

Who is most at risk for serious measles

Children under five years old have the highest rate of measles complications, especially those under one year. Adults over twenty also face increased risk. Pregnant women who are not immune can pass measles to their baby, causing birth defects or premature delivery. People with vitamin A deficiency, malnutrition, or weakened immune systems are more likely to develop severe measles.

Unvaccinated people of any age are at risk, but the youngest and oldest members of an unvaccinated community face the worst outcomes. This is why measles vaccination protects not just the person vaccinated but also vulnerable people around them who cannot be vaccinated for medical reasons.

How measles is diagnosed and what happens next

A doctor diagnoses measles based on the pattern of symptoms — fever, cough, Koplik spots, and the characteristic rash spreading from face downward. Blood tests can confirm measles by detecting antibodies or the virus itself, though diagnosis is often made clinically without testing. If you think you have measles, call your doctor before going in so they can take precautions to prevent spread to other patients.

There is no specific treatment that kills the measles virus. Care focuses on managing fever with acetaminophen or ibuprofen, staying hydrated, and resting. Vitamin A supplementation is recommended for children with measles, as it reduces the risk of complications. Most people recover at home, but hospitalization is needed if pneumonia develops, if you have difficulty breathing, or if you are at high risk for complications. You are contagious from four days before the rash appears until four days after it appears, so isolation during this time prevents spread to others.

Prevention through vaccination

The MMR vaccine protects against measles, mumps, and rubella and is given in two doses. The first dose is given at age twelve to fifteen months, and the second at age four to six years. Two doses provide lifelong immunity in about 97 percent of people vaccinated. If you were born in 1957 or later and have not been vaccinated or had measles, you should talk to your doctor about vaccination.

The vaccine cannot be given to infants under one year, pregnant women, or people with certain immune system disorders. People who cannot be vaccinated depend on others around them being vaccinated to stay safe. This is called herd immunity — when enough people in a community are immune, the virus cannot spread easily, even to those who cannot be vaccinated.

Frequently Asked Questions

Can you get measles twice?

No. Once you have had measles or been vaccinated, your immune system remembers the virus and protects you for life. Second cases of measles are extremely rare and occur only in people with severely weakened immune systems.

How long does it take to show symptoms after exposure?

Symptoms usually appear seven to fourteen days after you are exposed to the measles virus. Some people show symptoms as early as seven days, while others take up to twenty-one days. During this time, you can spread measles to others even though you feel fine.

Is measles the same as German measles?

No. Measles and German measles (rubella) are caused by different viruses and produce different rashes. German measles rash is lighter and does not follow the same pattern. The MMR vaccine protects against both, along with mumps.

What should I do if I think I have been exposed to measles?

Call your doctor or health department right away, especially if you are pregnant, have a weakened immune system, or are unvaccinated. They can advise whether you need the vaccine or other precautions. If you develop fever and cough within three weeks, call before visiting a clinic so staff can prepare.

Can adults who were vaccinated as children still get measles?

Very rarely. About 3 percent of people vaccinated with two doses do not develop immunity, though reasons why are not fully understood. If you are unsure of your vaccination status, a blood test can check whether you are immune.