B A G H D A D, Iraq, April 17 — Dangerous strains of cholera, black fever, HIV, polio, and hepatitis may have been lost during the post-war looting of Iraq's key disease control facility, ABCNEWS has learned. The U.S. military is worried they may be used as weapons. In an exclusive report on ABCNEWS' Good Morning America, Brian Ross revealed that scientists at Baghdad's central public health laboratory are worried that an unknown number of viruses have been stolen. They say looters took refrigerators full of the deadly viruses Friday, but they're not sure what's actually missing. "They are...