It was October 6, 2004, three years after Ernie Vallebuona's three-month stint as a rescue and recovery worker at ground zero in the wake of the 9-11 terrorist attacks, and he was hunched over and trembling, racked by a pain like nothing he had experienced in his 40 years of sound health. He had just returned to his Rockland County home after finishing the midnight-to-8 a.m. shift in the NYPD vice unit, where he'd reported to work for the last six years. Vallebuona had bought some fish from a street vendor near his office, on the Lower East Side. And as he drove the 35 miles from Manhattan to New City, he chalked up a searing stomachache to food poisoning. Maybe the vendor had filleted that fish with a dirty machete?