Measles is a highly contagious infection caused by the measules virus.Initial signs and symptoms typically include fever, often greater than 40 °C (104.0 °F), cough, runny rose, and inflamed eyes.Two or three days after the start of symptoms, small white spots may form inside the mouth, known as Koplik's spots. A red, flat rash which usually starts on the face and then spreads to the rest of the body typically begins three to five days after the start of symptoms. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days.Complications occur in about 30% and may include diarrhea, blindness, inflammation of the brain, and pneumonia among others.Rubella(German measles) and roseola are different diseases.

Measles is an airborne disease which spreads easily through the coughs and sneezes of those infected. It may also be spread through contact with saliva or nasal secretions. Nine out of ten people who are not immune and share living space with an infected person will catch it. People are infectious to others from four days before to four days after the start of the rash.People usually do not get the disease more than once. Testing for the virus in suspected cases is important for public health efforts.

Signs and symptoms:

The classic signs and symptoms of measles include four-day fevers (the 4 D's) and the three C's — cough, coryza (head cold, fever, sneezing), and conjuctivities (red eyes) — along with fever and rashes.Fever is common and typically lasts for about one week; the fever seen with measles is often as high as 40 °C (104 °F).Koplik's spots seen inside the mouth are pathognomonic(diagnostic) for measles, but are temporary and therefore rarely seen. Recognizing these spots before a person reaches their maximum infectiousness can help physicians reduce the spread of the disease.

The characteristic measles rash is classically described as a generalized red maculopapular rash that begins several days after the fever starts. It starts on the back of the ears and, after a few hours, spreads to the head and neck before spreading to cover most of the body, often causing itching. The measles rash appears two to four days after the initial symptoms and lasts for up to eight days. The rash is said to "stain", changing color from red to dark brown, before disappearing.Overall, the disease from infection with the measles virus usually resolves after about three weeks.