People who have an autism spectrum disorder (ASD) have problems communicating and interacting with others. Autism is one type of ASD. Autism symptoms often appear early, typically before age 3. Autism symptoms can include language delays; lack of eye contact; and repetitive or obsessive behavior, such as rocking or hand flapping. About 1 in 110 children in the U.S. has an ASD, and the symptoms can range from mild to severe.