Treasury Secretary Janet Yellen says China's slump has spillover risks but her US outlook is still positive

• Treasury Secretary Janet Yellen said China's economic snags pose some risks to the US. 
• "China's slowdown will have the largest impact on its Asian neighbors, but there will be some spillovers to the United States."
• But Yellen remains upbeat about prospects for the US economy.

Treasury Secretary Janet Yellen sees some risks for the US stemming from China's economic troubles, but she said she remains upbeat about the health of the American economy.