Only 20, or 4% of the 505 stocks in S&P 500 /zigman2/quotes/210599714/realtime SPX +0.30% are gaining ground in afternoon trading Monday, as fears the negative effects of escalating U.S.-China trade tensions drag down the broader market. The S&P 500 fell 2.8%, on track for a sixth straight loss and the biggest one-day decline since it shed 3.2% on Dec. 4. The biggest gainer is Tyson Foods Inc.'s stock /zigman2/quotes/201117502/composite TSN -0.33% , which rose 7.7% as better-than-expected earnings offset a disclosure of a Department of Justice subpoena. Next in line, shares of Jacobs Engineering Group Inc. gained 3.4% after earnings beat expectations. Meanwhile, among the S&P 500's biggest losers, shares of Fortinet Inc. /zigman2/quotes/205733290/composite FTNT +0.20% shed 7.0%, Tapestry Inc. /zigman2/quotes/207417762/composite TPR -1.51% gave up 6.8%, Wynn Resorts Ltd. /zigman2/quotes/208845907/composite WYNN +0.54% fell 6.6% and Nvidia Corp. /zigman2/quotes/200467500/composite NVDA +1.85% dropped 1.6%.