Stocks shook off earlier losses to trade higher as a positive quarter for Walmart (WMT) - Get Report and gains in the health care sector pulled indexes into the green. Wall Street closed with its worst losses in eight months a day earlier. Walmart, the world's largest retailer, posted earnings growth, while same-store sales in the U.S. increased by more than 1%. E-commerce business climbed at its best pace in five years. Nasdaq component AthenaHealth (ATHN) - Get Report rallied after activist investor Paul Singer disclosed a 9.2% stake. Elliott Associates' Singer said shares "are significantly undervalued." Alibaba (BABA) - Get Report declined as investors focused more on weaker earnings over its fourth quarter than a massive surge in revenue. The Chinese e-commerce company missed profit estimates by three cents, though sales rocketed 60% higher and beat consensus.