The president’s top health official is calling on the nation to “rededicate” itself to addressing the needs of those with autism.

Health and Human Services Secretary Kathleen Sebelius called autism “an urgent public health challenge” in a statement marking the start of autism awareness month in April.

“Over the last decade, we’ve learned that autism is far more prevalent than we had previously believed,” Sebelius said. “While we still have a lot to learn about what causes autism and which treatments can help people with autism thrive, we’re getting closer to finding answers.”

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Friday evening a number of notable buildings around the world will be lit blue in honor of autism awareness. The Empire State Building and the Willis Tower — previously known as the Sears Tower — are among the landmarks scheduled to participate.

A series of walks, fund-raisers and other awareness events will highlight the remainder of the month.