Measles is a highly contagious infection caused by the measles virus. Initial signs and symptoms typically include fever, often greater than 40 °C (104.0 °F), cough, runny nose, 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.