TSC Ratings provides exclusive stock, ETF and mutual fund ratings and commentary based on award-winning, proprietary tools. Its "safety first" approach to investing aims to reduce risk while seeking solid outperformance on a total return basis.Earnings season looks more like flu season as sneezing health care stocks sickened the performance of exchange-traded funds. During the five trading days that ended Thursday, the 79 health care ETFs we track lost 2.9%, on average. The only exception was the ProShares UltraShort Health Care Fund ( RXD), which sells the sector short to generate an inverse performance. The S&P 500 Index was little-changed during the week. The worst-performing health care fund was the Rydex 2X S&P Select Sector Health Care ETF ( RHM), which dropped 6.8%. The fund's two largest holdings Johnson & Johnson ( JNJ) and Pfizer ( PFE) slipped 1.5% and 4.5%, respectively. One of the fund's biggest losers was Thermo Fisher Scientific ( TMO), which gave up 13%. The company's first-quarter earnings fell 49% from a year ago, ending a nine-year streak of profit growth. Thermo Fisher also cut its 2009 earnings outlook. Another holding, Biogen Idec ( BIIB), lost 11% over concerns that its multiple sclerosis drug Tysabri might be linked to a potentially fatal brain infection. The company recently confirmed that a sixth patient contracted the disease since the drug returned to the market in July 2006. The disclosure casts doubt over future sales of Tysabri and raises legal questions. The ProShares Ultra Health Care Fund ( RXL) and the ProFunds Health Care UltraSector ProFund ( HCPIX) had the second- and third-biggest declines of the group. Both portfolios aim to track the daily performance of the Dow Jones U.S. Health Care Index with 200% and 150% leverage, respectively.