Measles symptoms usually appear 7 to 14 days after contact with the virus. Measles typically begins with:

• High fever (may spike to more than 104°)
• Cough
• Runny nose (coryza)
• Red, watery eyes (conjunctivitis)

Tiny white spots (Koplik spots) may appear inside the mouth two to three days after symptoms begin.

Measles rash appears 3 to 5 days after the first symptoms. It usually begins as flat red spots that appear on the face at the hairline. They then spread downward to the neck, trunk, arms, legs, and feet. Small raised bumps may also appear on top of the flat red spots. The spots may become joined together as they spread from the head to the rest of the body. When the rash appears, a person's fever may spike to more than 104°F.

Measles is an airborne disease and is spread when an infected person coughs, sneezes, or talks. It is one of the most contagious illnesses that exists; as many as 9 out of 10 close contacts who have not had the disease earlier or have not been vaccinated with the MMR vaccine may become infected if exposed. After an infected person leaves a location, the measles virus remains alive for up to two hours on surfaces and in the air.

Some people who contract measles may suffer from severe complications, such as:

• Hospitalization: About 1 in 5 unvaccinated people in the U.S. who get measles is hospitalized.
• Pneumonia: Pneumonia is the most frequent serious complication, often resulting in hospitalization.
• Encephalitis: About 1 in 1,000 people who get measles will develop encephalitis (swelling of the brain), which can lead to permanent brain damage or death.
• Subacute sclerosing panencephalitis (SSPE): SSPE is a very rare, but fatal disease of the central nervous system. It results from a measles virus infection acquired earlier in life.
• Complications during pregnancy: In pregnant women who have not had the MMR vaccine, contracting measles significantly increases the risk of miscarriage, premature labor, and low-birth-weight in newborns.
• Blindness: Measles can lead to or exacerbate vitamin A deficiency. Blindness as a complication of measles is usually due to damage to the cornea as a result of this vitamin A deficiency.
• Death: Although death is uncommon in adults, between 1 and 3 of every 1,000 children who become infected with measles will die from respiratory and neurologic complications.

Another lesser known, but far more widespread, complication of measles is called "immune amnesia." Immune amnesia is a condition where the immune system "forgets" previously acquired immunity following a measles infection. Immune amnesia can erase up to 73% of a person's immune memory, making it harder for the immune system to fight off infections, including those that a person has previously had. This condition can last for two to three years following a measles infection.

It is important to note that, whereas contracting the measles virus can adversely affect immune system functioning, the measles vaccine has the opposite effect, helping to strengthen the immune system.

The best way to prevent the spread of measles is vaccination. The MMR (measles-mumps-rubella) vaccine is very safe and effective. Two doses (the recommended dosage) of the measles vaccine are about 97% effective at preventing measles if you are exposed to the virus. One dose is about 93% effective. Conversely, unvaccinated individuals have a 90% chance of contracting measles when exposed to the virus. For more information, please see DPH's measles vaccine guidance.